I’m assuming you mean for the Fall quarter? Or are you referring to summer move in?
Either way, it is not really possible to move in early, unless you are part of a program/job/group that needs special permission to move in early, like the FSSP students or staff among others. I haven’t heard of any (just) students moving in early.
For your first question: the rooms are basically up for grabs. The first person to get in there is the one who gets the pickings for the spots, beds, etc. The only pre-picked aspect is the room, but everything inside depends on you and your roommates.
Also, you can move furniture around (as long as you’re not throwing stuff out that belongs to the university or damaging stuff). Beware, if you’re in a double and move furniture around, you WILL be required to put everything back the way it was on move-in day. If you’re in a triple, they might ask the same of you.
I saw from previous threads that you’re a transfer student. So that means you’re referring to the university apartments?
The apartment policies might differ slightly from what I’ve said. For the most part, they should be the same.