I don't know that I have ever stated Adam had a different "nature" before or after the fall. Only that the nature Adam had after the "eyes were opened" was no longer pure and undefiled. Adam was defiled, Abraham was defiled. The seed that anointed Mary's egg (to be rather graphic) was not of Adam nor of Abraham, but of the Word of God. In that conception, it follows that Christ was as the Eden Adam (before the fall) in that the human nature of Christ was without sin, capable of being tempted to sin (just as Adam was when presented the fruit by Eve), but remained undefiled to the cross.
First of all, Adam and Eve could be tempted just like us. Their nature was no different than ours.
Adam did not have God's nature, because God cannot be tempted.
Jam 1:13 Let no man say when he is tempted, I am tempted of God:
for God cannot be tempted with evil, neither tempteth he any man:
A person can attempt to tempt God, but it will have no effect upon him, he has no internal lust or desire that would tempt him to do evil.
Jesus on the other hand had the same nature we have. He was actually tempted to sin just as we are. The scriptures say he "suffered" being tempted.
Heb 2:16 For verily he took not on him the nature of angels; but he took on him the seed of Abraham.
17 Wherefore in all things it behoved him to be made like unto his brethren, that he might be a merciful and faithful high priest in things pertaining to God, to make reconciliation for the sins of the people.
18 For in that he himself hath
suffered being tempted, he is able to succour them that are tempted.
When Jesus fasted 40 days, the scriptures say he was very hungry. He felt this hunger, he wanted to eat. This is why the devil tempted him to turn stones into bread. Jesus had the same infirmity or weakness of flesh that pulls and tugs on us. God does not get hungry, he could not be tempted like this.
Heb 4:15 For we have not an high priest which cannot be touched with the
feeling of
our infirmities; but was
in all points tempted like as we are, yet without sin.
The scriptures say Jesus was tempted in ALL POINTS as we are. He felt the same pull and tug of the flesh that we feel, yet he never sinned. God does not feel the tug and pull of the flesh.
Adam and Eve were no different than us, the three lusts of the flesh are described in her temptation.
Gen 3:6 And when the woman saw that the tree was good for food, and that it was pleasant to the eyes, and a tree to be desired to make one wise, she took of the fruit thereof, and did eat, and gave also unto her husband with her; and he did eat.
Eve saw that the tree was good for food. This is the lust of the flesh or the appetite. We get hungry when we see good food, this is what Eve felt.
Eve saw the tree was pleasant to the eyes. We are all attracted to beauty, many a man has fallen into sin because he saw a beautiful woman and desired her.
Eve saw the tree would make her wise, this is the pride of life. We all want to be intelligent, often we want to be smarter than our fellow man so we can boast or feel proud.
Now, did Eve feel these temptations before the fall or after? BEFORE! Adam and Eve were always flesh and could always be tempted. They were no different than we are today.
The curse was on the ground, everything began to grow old and decay. Animals who cannot sin died, even non-living things grow old, rust and decay, stars burn out, etc... This was the curse. There is not one word concerning man's moral nature being affected by the curse, you can't show it here or anywhere in all of scripture.
The curse was actually a good thing, for if man lived forever as a sinner he would simply become more and more corrupt. It is because we know we will die and face judgment that we repent and trust Christ. If we lived forever, I doubt any man would turn from sin and trust Christ.
So, Adam and Eve were always flesh, yet they were very good, because they had never sinned. It is when a man sins he becomes a sinner.
Jesus received his flesh from his mother Mary and could be tempted. God is a spirit and cannot be tempted. Jesus had the same nature as Abraham and was tempted in all points as we are, yet he never sinned.