When giving a noble multiple rooms, do I need to assign each of them separately?

So most nobles require their own bedroom, dining room, study, and sometimes even a tomb, armour stand and what not. About designating and assigning rooms:

• Do I need to create and assign each of these separately?
• Do they need to be actual separate rooms, or can each piece of furniture be in the same room?
• If rooms are to be separate, should separating doors be set as "internal"?
• Does any of this make a difference in dwarf happiness?