In the Godfather part II, did Roth have Michael killed because of Moe Green?

Also I've tried to follow the Godfather part III but I don't understand why Altobello and Luchese wanted Michael killed.

Also did they have the newly elected Pope killed as well? And what new Pope was going to be elected that was not a friend to the Coleone family? The clergy that we see Michael having conversations with about the 700 million debt?