u/Frost033

I have a dedicated server for a few of my family and friends to play on. Me and my buddy play more than other people and are outpacing the other 3 in level. So as we progress I was wondering a few things

1. Can quests could be redone by people who haven't done them so they can earn that XP as well? If they can, are they harmed by me being there with them at a higher level or having done the quest already?
2. I've noticed and read that XP is higher in your first encounter in a POI, is that a 1 time deal, or is it first encounter for that character?
3. Is there a way to level them up faster to catch up? Does being in the area when we kill higher level's give more xp?

I feel like this makes playing the game with friends difficult when some can play more than others. But maybe I'm mistaken in how it works? Thanks for any help/advice you can give.