Yes I believe we have lived many lives, and I feel when we keep coming back we are trying to get to that place where we are Christ like in all we think, say and do. We have lessons to learn and we can not possibly learn them in one live time. Have you ever had a feeling so strong about doing something or saying something you could swear you have done it before, it's because you have and in a past life you may have chosen one way of doing it and in this one you may try to do the opposite and get a different out come.
You will know when it happens, because you have a strange feeling you can't explain and your heart races, there's always a sign if you pay attention.You have the option to try to understand what's going on and if you can be still in that moment you can see it and know what happened, so you can choose to experience it again or go about it differently this time, it's up to you. Keep in mind it is a lesson, so live it, learn it and grow.
I don't know. It's shifty business. I'm Christian, and I don't know what the Bible says about this. There was a little boy recently who claimed to remember his past life, and his parents believed him. So I don't know. Personally I love the show "angel beats."