you cant recruit arceus he ain't a recruited Pokemon but when you get a space globe from his statue in destiny tower
Nope
he is a fake
Yes
they ask you if they can be on the tam
you recruit him by going to electric plateau
No, there isn't.
If you're talking about Pokemon Mystery Dungeon Explorers of Time or Pokemon Mystery Dungeon Explorers of Darkness, you can recruit as many Pokemon as you want. If you are talking about Pokemon Mysatery Dungeon Blue Rescue Team or Pokemon Mystery Dungeon Red Rescue Team, you can only recruit a certain number of Pokemon per friend area.
mission recruit or egg
in the second cave
no but you will find the statue of arceus
dungeon leader can be any Pokemon you recruit. you will be able to change leading Pokemon after you graduate .
concealed ruins with secret slab or mystery part