SEVEN DAY WEEKS ARE A HUMAN CONSTRUCT—OR ARE THEY? The Bible Speaks Of The Creation Having Been Created In A Six Day Period. The following day God rested from His work of Creation and this suggests seven periods, which are called days.
Not sure whether this is meant to be two questions or one. I will assume that it is meant to be one question: Apart from the 7th day of the Creation Week was there a 7th day before the 10 Commandments?
The short answer is wherever there was a calendar, there was a seventh day of the month. The Sumerians and, Egyptians divided each month into 30 days. Once every month there was a 7th day. 
Somehow, though, the implication appears to be that this is probably meant to be two questions that incorporate the following two thoughts:
Was a seventh day Sabbath kept where people did no work and focused on worshiping God before the 10 commandments?
Is the seventh day of the Creation week a literal 24 hour day?
The Seventh Day of the Creation Week, according to the Bible, has no evening. Hence it has not ended. For when we read what is written in the Bible, we read:
And God saw everything that he had made, and behold, it was very good. And there was evening and there was morning, a sixth day. Thus the heavens and the earth were finished, and all the host of them. And on the seventh day God finished his work which he had done, and he rested on the seventh day from all his work which he had done. So God blessed the seventh day and hallowed it, because on it God rested from all his work which he had done in creation. These are the generations of the heavens and the earth when they were created. In the day that the Lord God made the earth and the heavens. (Genesis 1:31–2:4)
You will not find anywhere in the Bible where the seventh day of Creation ended and the eighth day began.  What you will find is that in the day the Lord God created the Heavens and the Earth there were seven periods marked off—not nine periods of time, which is required for there to be seven complete days. The first period has no beginning and the seventh period has no ending. How do we know that this Creation Week is ONE DAY? Because the Bible tells us that this is the case in the second chapter of Genesis:
These are the generations of the heavens and the earth when they were created in the daythat the Lord God made the earth and the heavens. (Genesis 2:4 above)
When you remove the punctuation from the English—which is not in the original languages—the message is easier to understand. Chapter divisions with verses and punctuation is one of the reasons truth is even more difficult to uncover than it need be—thus we need to be taught by the Holy Spirit. (Pray to be taught the truth daily.)
Currently, we are still in the Seventh Day of Creation as is evident from the above quotation from Genesis, since God has not ceased resting from the works of Creation of the Universe. In the following quotation from the book of Hebrews, not only is it evident that God is still resting from His works of Creation but also that we are instructed—if wise—to do our utmost to enter His rest. For we read:
For we who have believed enter that rest, as he has said, “As I swore in my wrath, ‘They shall never enter my rest,’”although his works were finished from the foundation of the world. For he has somewhere spoken of the seventh day in this way, “And God rested on the seventh day from all his works.” And again in this place he said,“They shall never enter my rest.” Since therefore it remains for some to enter it, and those who formerly received the good news failed to enter because of disobedience, again he sets a certain day, “Today,” saying through David so long afterward, in the words already quoted,“Today, when you hear his voice, do not harden your hearts.” For if Joshua had given them rest, God would not speak later of another day. So then, there remains a Sabbath rest for the people of God; for whoever enters God’s rest also ceases from his labors as God did from his. Let us therefore strive to enter that rest, that no one fall by the same sort of disobedience. (Hebrews 4:3–11)
There is no evidence in the Bible that anybody, other than those to whom Moses gave the Ten Commandments and their descendants according to the flesh, has been instructed to observe the seventh day of the week as the Sabbath Day—absolutely none! Note what Moses said to the Israelites:
“‘Observe the Sabbath day, to keep it holy, as the Lord your God commanded you. Six days you shall labor, and do all your work; but the seventh day is a Sabbath to the Lord your God; in it you shall not do any work, you, or your son, or your daughter, or your manservant, or your maidservant, or your ox, or your ass, or any of your cattle, or the sojourner who is within your gates, that your manservant and your maidservant may rest as well as you. You shall remember that you were a servant in the land of Egypt, and the Lord your God brought you out thence with a mighty hand and an outstretched arm; therefore the Lord your God commanded you to keep the Sabbath day. (Deuteronomy 5:12–15)
When we read what Moses said to the Israelites, we see that the reason they were to observe the Sabbath was because they were a servant in the land of Egypt and God has rescued them.
Say to the people of Israel, ‘You shall keep my Sabbaths, for this is a sign between me and you throughout yourgenerations, that you may know that I, the Lord, sanctify you. (Exodus 31:13)
Abraham is said to have kept God’s commandments (Genesis 26:5). Did this include the Sabbath? There is no mention of the Sabbath at all, even though the Abraham’s descendants are mentioned:
I will multiply your descendants as the stars of heaven, and will give to your descendants all these lands; and by your descendants all the nations of the earth shall bless themselves: because Abraham obeyed my voice and kept my charge, my commandments, my statutes, and my laws.” (Genesis 26:4–5)
What we find, though, when we read the context of Moses’ statement in respect to why the Israelites had to observe the Sabbath Day as a perpetual sign, because they had been rescued from Egypt via the Red Sea, the Fathers were not given a covenant to observe the Sabbath.
And Moses summoned all Israel, and said to them, “Hear, O Israel, the statutes and the ordinances which I speak in your hearing this day, and you shall learn them and be careful to do them. The Lord our God made a covenant with us in Horeb.Not with our fathers did the Lord make this covenant, but with us, who areall of us here alive this day. The Lord spoke with you face to face at the mountain, out of the midst of the fire, while I stood between the Lord and you at that time, to declare to you the word of the Lord; for you were afraid because of the fire, and you did not go up into the mountain. (Deuteronomy 5:5)
Who are the Fathers? Moses was told who the Fathers were when he was first commissioned by God to go to Egypt and become His Apostle.
God also said to Moses, “Say this to the people of Israel, ‘The Lord, the God of your fathers, the God of Abraham, the God of Isaac, and the God of Jacob, has sent me to you’: this is my name for ever, and thus I am to be remembered throughout all generations. (Exodus 3:15)
Evidently, Abraham, Isaac and Jacob had not entered into a covenantto observe the Ten Commandments as given to the Israelites, who had been rescued from the land of Egypt. Even though they were the Fathers of the Israelites and had entered into covenants, there is no record of them having been required to observe the Sabbath Day, one day in every seven days as a day of rest.
From the what is written in the Holy Scriptures of the Israelite canon as delivered by Moses, there appears to be no covenant requiring the seventh day to be observed every seven days. This is peculiar to the Israelites who were rescued from Egypt. However, since Abraham did keep all God’s commandments, he obviously obeyed God’s voice and entered the Sabbath Rest of his Lord and Savior, which is what we are called to do in the book of Hebrews 4:11 (strive to enter God’s rest), as quoted above.
There has always been a Seventh Day Sabbath Rest for God’s people—that is, those who enter it experience this rest. The Israelite nation was commanded to observe every seventh day along with other Sabbaths—which fell on the first day of the week—and appear before the Lord God. This is because the covenant that was given to Israel as a nation was different to the covenant that was given to Abraham or Isaac or Jacob, the Fathers. We who enter God’s Sabbath, do so under the Abrahamic Covenant and not that given to the Israelites known as the Mosaic Covenant. Therefore we do not have to keep a Sabbath Day once a week as a sign of our salvation, rather we are to observe what Abraham did (John 8:39). We read:
The promise to Abraham and his descendants, that they should inherit the world, did not come through the law but through the righteousness of faith. If it is the adherents of the law who are to be the heirs, faith is null and the promise is void. For the law brings wrath, but where there is no law there is no transgression. That is why it depends on faith, in order that the promise may rest on grace and beguaranteed to all his descendants—not only to the adherents of the law but also to those who share the faith of Abraham, for he is the father of us all. (Romans 4:13–16)
The mistake too many people make is that, first, they see the Seven Days of Creation as twenty-four hour days. Second, they equate the Ten Commandments as given to Israel as a covenant binding upon everyone. Third, they do not understand what a covenant means.
If you understand that covenants are agreements that are made between particular individuals that contain specific conditions, then you will be able to understand why there are so many divine promises made establishing or modifying God's relationship with various individuals and groups of people as recorded in the Bible.
Essentially, many of the covenants are not just specific to the individuals involved, they are also a progressive revelation of salvation truth. For instance, the covenant made with Noah before the flood is later modified after the flood to include every person and every creature.
But I will establish my covenant with you; and you shall come into the ark, you, your sons, your wife, and your sons’ wives with you. (Genesis 6:18)
“Behold, I establish my covenant with you and your descendants after you. (Genesis 9:9)
Likewise, the Mosaic Covenant (if you are open to the truth) in respect to the Sabbath Rest is modified through Isaiah when he prophesies in the power of the Holy Spirit:
Nay, but by men of strange lips and with an alien tongue the Lord will speak to this people, to whom he has said,“This is rest; give rest to the weary; and this is repose”; yet they would not hear. (Isaiah 28:11–12)
This rest is found in the Son of God. This is the commandment of old that many overlook when they throw out the baby with the bathwater and pick and choose what Scriptures they will consider and what they will dismiss.
Yet who knows the plumb line? Many use a defective plum line. How can people build truth without the true plumb line? Did not Jesus say people who build and do not count the cost will be laughed at? So how does one build without a plumb line?
A plumb line was essential for building before the days of levels and lasers. A plumb line is still essential if we are to learn the truths of God and build a buttress for the fortress of truth, which can withstand the deceptions of the Devil, and correctly interpret the WORD of GOD in our own lives (so that we do not come up with false teachings). 
Those who understand the only words written by God are the ones who can build a true understanding of what is really written in the Bible, and why the Melchizedek Order’s ways surpassed the Levitical Order. This Abraham did. This is why he entered the true Sabbath, obeyed God’s voice, charge, commandments, statutes and laws. Only the shortsighted get hung up on the day and miss the truth, whereas the blind throw out the Old Testament not realizing that this contains the truth of God’s plan.