Hi enlightened,
We know from reading the Bible, that God is eternal and knows everything. Why else would the Trinity agree to the plan of redemption before the foundation of the world? I would hold that God knew very well what Adam and Eve would do. He permitted it, just as He permitted Satan to take everything from Job except his life. Why did God allow the freedom of choice?
Romans 11:32
New King James Version (NKJV)
32 For God has committed them all to disobedience,
that He might have mercy on all.
I'm not sure what promise you refer to when you said, "then HIS promise to Adam of a perpetual life for obedience to the Commandment," but if that promise was made, it was answered in Jesus Christ who is our perpetual righteousness.
1 John 3:19-20
New King James Version (NKJV)
19 And by this we know[
a] that we are of the truth, and shall assure our hearts before Him. 20 For if our heart condemns us, God is greater than our heart,
and knows all things.
1 Peter 1:20
New King James Version (NKJV)
20 He indeed was foreordained before the foundation of the world, but was manifest in these last times for you
- Davies