Regarding a seventh day . . . your citation seems to be irrelevant. There is no place in the pre-Mosaic covenants that a special day of religious observation is mentioned, or even hinted, AFIK. On the seventh day of the Creation episode, God rested. It doesn't even hint that Adam also rested, does it? Unless it was when he was anaesthetized for the removal of a rib. Hmm?
That's only because you're viewing it through the prism of the modern day notion that Jesus abandoned the sabbath that he created.
Genesis 1:14 shows that one of the primary reasons for the creation of heavenly bodies was to allow man to know WHEN God's sabbaths are. The Good News Bible puts it this way:
(GNB) Then God commanded, "Let lights appear in the sky to separate day from night and to show the time when days, years, and religious festivals begin;
You may be familiar with something like the King James where it says:
(KJV) And God said, Let there be lights in the firmament of the heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years:
The word translated "seasons" isn't winter, spring, summer and fall...but is indeed the very same word which refers to God's holy days...including his sabbath. Literally it's "appointed times".