One Login for multiple themes possible?

Hi,

I currently own only one premium press theme (Classifieds) but I plan on getting the business directory theme as well. I have a couple of question regarding multiple themes.

1. All premium press theme are wp multi site compatible, correct?
2. Is it possible to use one login for both themes (interchangeable login / logout form) in a multi site configuration?

If number 2 is not currently possible, then will this be implemented in version 9?

Thank you
Brian