An interesting point in Genesis 2:4, "These are the [generations] of the heavens and of the earth when they were created, [in the day] that the Lord God made the earth and the heavens."  I'm not sure what a generation of that kind is.  How can the earth or heaven have generations.  Unless it is repeated restorations. And also, the phrase, "in the day."  Seems like a poor translation???  Which sometimes happens.  I try to look at things that I don't understand in a number of Biblical translations.

The four trees in the garden of Eden were important.  Two were for us to enjoy.  The flowering trees (pleasant to the sight), and fruit trees--food to eat.  Genesis 2:17, "But of the tree of the knowledge of good and evil, you shall not eat of it: for in the day that you eat thereof you shall surely die."  The reason that God cast them out of the garden when they disobeyed is because God didn't want them to eat from the tree of Life. "And the Lord God said, Behold, the man is become as one of us, to know good and evil: and now, lest he puts forth his hand, and takes also of the tree of life, and eat, and live forever." 3:22

You may wonder why Adam and Eve didn't physically die when they disobeyed.  God wasn't talking about physical death.  He was talking about Spiritual death.  Remember he had breathed into man the breath of Life.  A living soul.  After sin, they would no longer have the Spirit within.  Paul said, "And he has quickened you who were dead in trespasses and sins." Ephesians 2:1

Quickened:  Made alive.  God intended to live within the soul of man.  The Old Testament tells of a coming Messiah.  It assures us that God will restore us.  He, Himself will come as a sacrifice for our sins.  Jesus.  The Spirit of God will once again inhabit us.  Why would He do that?  The only possible answer is love.  He loves us.  Why in the world does He love us?  That's the real question.

When Adam and Eve ate of the tree, they saw that they were naked.  They didn't know they were naked before that.  So they covered their sexual parts with an apron of leaves.  When God came to confront them, He sacrificed an animal to cover them.  That was the first sacrifice.  Up till that moment, no animal had been killed. God said, "Who told you you were naked?...What have you done??"  Then, "...the Lord God made them coats of skins, and clothed them."  From that point on, a sacrifice was required for sin.  Goats, sheep, doves, and eventually Christ.  God himself.