Question 1: I imagine you can choose from a creature database. Or there will be a feature that lets you make a creature then and there, no need to collect DNA points or anything. Your creatures' aggression and socialness may be sliders you choose from then.

Question 2: Yes, there will still be computer creatures on your planet throughout civ and space phase. Creatures you make in the space phase may be deployed in little zoos and moved about by your UFO. You probably won't be able to get in their heads and directly control them, though.

Question 3: Yes, you can get out of your UFO. What is you can actually do is so far unknown, however.