QUESTIONS: Did God only create Adam and Eve at first or were there more people?

God created Adam and Eve as adults (not newborns). Why couldn’t He create an earth that is “old” also (I.e. not new ) in a literal 7 days?

Why the tree in the garden? Free will?

Does the Bible allude to what this means: Genesis 9:5 "I will demand an accounting from every animal". What does it mean?

Is it possible that Cain and Able might have been twins?

What does it mean to be out of gods grace. When Cain left, he left God's grace what does that mean.