Qs about national heroes and prophets

[FNC]

My prophet dies Last turn. Dies does not really explain it. He was clobbered/decimated/destroyed! I was careless and lost him. He was also one of my national heroes.

1) When can I assign a new prophet?? The option is not currently there for other commanders(and the prophet is definitely dead!).

2) Do national heroes ever come back to lie or will I never see him again??

3) Can you have more than 1 national hero(and I don't mean duplicates)??

Thanks!