For the fourth question: So, you have to go all the way back to start a new route?
You could load an earlier save and continue from there, if you have one.
You can also use the Chapter Select feature to start a new save from a later point in the game, if you'd like to skip over repeated content.
If none of those options suit you, you can start a new save from the beginning and use the "skip" feature to skip past dialogue you've already seen before.