It could be a conviction for immigration purposes and certainly it will come up if you wish to return to the U.S.

It depends on the country. Contact the embassy and ask.

It depends what kind of visa and why you need it extended.

It depends what it says. If it says your visa is revoked, then your visa is revoked. If it says your prior employer withdrew the visa, then...

I am not aware of any law that prevents you from traveling on a different passport with your green card.

It depends on what you did that caused you to fall out of status.

Without knowing your whole immigration history, it is not possible to say whether it is safe or not. But based on your description I don't see any...

It seems to me that the answer is no. Withdrawing an application to change or extend status is not the same as being denied a visa.

They might know. They might be looking for you if you meet their priority criteria.

It should not have any impact on one's immigration to the U.S.