1. Yes, flip and change are the same.
2. Whatever feels right for the fiction. I know that's sort of a hinky answer but it's really dependent on the narrative like a lot of PbtA stuff. Running from the fight for a better position, having to fall back from a powerful assault. That sort of thing.
3. Whenever the GM says it's over. We did three rounds, fourth for a tie breaker and it was over during playtests.
4. Again, this depends on the GM and the fiction. As the book says, the GM sets the prizes for winning.
5. The former.
6. Also the former.