Just by the logic of your theology, what is the point of giving Moses laws when he already gave it to Adam and Noah, why not just pass it down from there?
They weren't the same laws, and they were passed down, e.g., marriage, was given to Adam and referenced by the Lord, and expounded to Moses, and referenced by the Lord; likewise, capital punishment and food laws, were given to Noah and referenced by the Lord, and expounded to Moses, and referenced by the Lord, etc.
All these expansions (revelations) of how God wants man to live, were ever increasing, to the point of the inevitable manifestation of His Son, Who expounds God's law perfectly--teaching us to do it from the heart, not by outward motivation, but by the love toward God.
This ultimate magnification of God's laws, by Christ, is obvious in all that He said and taught: for example, to Moses, God commanded that any committing adultery must be put to death, yet the Lord says, that any who look on a woman, to lust after her, has already committed adultery with her in his heart! That expansion of God's law, is now passed down to us!
The Lord did not come to reduce the law, but expound on it's righteousness, teaching us, that all of it, originates in the heart, and thus, we must repent, and be born again, to serve God from our love toward Him, not from our fear of man.
To love God is to keep His commandments, all of them--which are way more than 613, lol, seriously tho, way more--without number in-fact: for anything we do, we must do it to the glory of God, and those of us who love Him, do the righteousness of the law, and we are not limited by the letter...
(In saying all that, I know that I've exposed myself not to be in accord with most, but with respect, I couldn't care less: I fear the Lord.)
Fear God and keep His commands folks, especially the ones not written down!
Hallelujah!