If adam and Eve had not sinned would we never have had sin?

Actually, all human beings are created with free will, so even if the first humans had never sinned, subsequent humans would still have to decide for themselves whether to obey God or do their own thing. And, in fact, each of us does have to make that decision many times during our lifetime on Earth.

They didn't sin.  Before eating the forbidden fruit, they didn't know it was wrong to disobey God.  There was no original sin.  Our own sins suffice for our own falls from grace.

If Adam and Eve had not eaten the forbidden fruit eventually, God might have thrown them out of the Garden on a technicality -- failure to fill the Earth.  His plans are not so easily derailed. 

Mortality, fertility, and cognizance of Good and Evil were not disasters, but necessary developments for our species.  Nor was Adam punished for his transgression.  It certainly SEEMED like it to Adam, but it really was for his sake that he was cast out of the Garden.  We need problems to overcome, or we'd never get anything done.

The Bible states that all have fallen short of the glory of God.

That means we all sin.

If Adam and Eve never sinned then someone else would of.

Romans 3:23 “For all have sinned, and come short of the glory of God;”

And 'rib-woman' spoke to a talking serpent in Mesopotamia.

"ssss".

That's a hypothetical question. Nor can you compare humans on a sinless, perfect Earth with spirit creatures who were perfect until they chose to sin. Consider: if the first rebellious spirit creature who later became know as serpent, devil, satan, dragon, had not tried to get the first humans to sin against God, might he not have tried a bit later with Adam and Eve's children? Or, if that evil one had given Earth a total body-swerve permanently, would Adam and Eve had sinned at all?

But you are wrong to assume that "After the flood Noah and his three sons were good." No. They were not. They had already sinned, as had all other humans before the Flood struck. Jesus clearly told us that no-one is good except God alone. Don't mix up being an apparently 'good' person with being sinless. Nobody is sinless, hence nobody is 'good'.

Yes, the initial sin in the garden of Eden, and later sin after the Flood, happened for a reason. To prove to us sinners that we cannot avoid sin because we have a sin nature after Adam and Eve sinned. Even if we had been like A&E, sinless and perfect, we could still be tempted to disobey God, as were they.

It's a myth, seriously.  :)

The Bible's take on Adam and Eve is just the retelling of an ancient Semitic myth.

When you give someone a choice you take the chance they will choose the wrong way.  When you take away the choice, you take away their freedom to chose.

If the Autobots had not come from Cybertron and landed on this planet would we never have gotten involved in the war with the Decepticons?

Somebody else would have messed up.