...believe in one god right? Seeing as how theres many cultures that have several gods, wouldn't that knowledge be passed down and corrected right off the bat?
Adam and Eve is true.
In reading the true and complete text of the Holy Bible you would understand with clarity the reasons for events and how they unfold.
free will
and the introduction of sin.
No because each person has individual choices and ability to decide for themselves what is right. Do you believe everything your parents do? I know I don't. That's why Jesus is beautiful. We have our own choices to make.
As far as there being more than one god, people make up things they think will make them feel better.