there is a term for when you meditate and suddenly you feel clear like water for just a split second or something. what is it?

I think there's a Pali term. But here in Thailand they use just some common term like 'got deep in meditation' or something. 'Feel enlightened' (feel clear and knowledgable) may also be used by Thais to describe this stage of peak in meditation.
(when you reach nirvana, you will never have to be born again.
sampajanya is consciousness but use in other context)

#4 -- I'm no expert, but I think so. It's release from the wheel of reincarnation into this illusory world. Once you're off the wheel, you have pretty much ceased to exist as we understand existence, so there's no one there that could get back on the wheel and still be you.
The Bodhisattvas came as close to nirvana as you can get without getting there, but didn't take the last step in order to help the rest of us get there. As I understand it.
Edited by: Avalokiteshvara

Let's hope the thousand arms doesn't interfere with Shiva, Vishnu or anything to do with Taoist mythology...