Question about gaining EXP points

Hello I got a couple of questions regarding the EXP points system.

1. If I’m currently level 10 and I do a quest that is level 8 ( so it’s green for me) will I get the same amount of EXP as if I’ve done the quest while being level 7 or 8 ( also green but not overleveled by 3 levels)

2. Similar question to the first one but about red quests. What if I made a quest that is red for me? Would I get more EXP?

3. Scavenger hunt quests – do they grant EXP? I’ve read that the quests don’t give you EXP per se but you get some during them for collecting diagrams. Is that true?

I ask because I wonder how on earth people finish the same game doing all the stuff and one person is level 35 and one is 42 for example ( based on forum information). Will I get different EXP points for doing a level 8 quest when I’m level 6 , different when I’m level 8 and different when I’m level 13 for example lol.? Or do you get the SAME amount of EXP as long as the quest is green for you? I know that deathmarch gives you less EXP but that’s not what I’m asking about. I’m asking about the mechanics of exp granting regardless of difficulty level.

Question about gaining EXP points