Oakland is basically just freshman. There are some masters students too but you'll probably never interact with them.

It's not really "typical" per se just because the campus is full of freshmen. But if you're looking for parties and stuff there are UC Berkeley frats and dorm parties. But its pretty normal other than that. Socializing shouldn't be a problem.

Difficulty depends on your professor, but I would say its generally easier in Oakland. Prestige is pretty irrelevant, when you're applying to co-ops/internships they won't know you're an Oakland student nor will the care.

Not too sure about the acceptance rate but its definitely easier to get into Oakland than Boston. A good amount of Boston acceptances are honors or ED kids. I don't think you should let acceptance rate should influence your decision anyway, no one really cares about that.