Genesis 2:15-17
15 The Lord God took the man and put him in the Garden of Eden to work it and take care of it. 16 And the Lord God commanded the man, “You are free to eat from any tree in the garden; 17 but you must not eat from the tree of the knowledge of good and evil, for when you eat from it you will certainly die.”
He was only forbidden from partaking of one tree. I don’t think there was anything special about the Tree of Knowledge, other than it was a gateway sin to all the other sins of mankind.
My essential understanding is that you need continual access to the Tree of Life in order to live forever. A one-time access will only hold off death for whatever time the fruit is good for. It’s vitamins and minerals, you need a continual supply in order to stay healthy.