I'm not Steve...but:
1. Not with Personas 3.0 - only Personas 2.0 can do that
2. As a consequence of #1, in Personas 3.0, the answer is yes. With Personas 2.0, no - you can have it installed in a separate, so-called "main system" and connect it to other systems, but this is not the recommended way.
In case you want to use Personas 3.0 in a system that's on NW 731, you may be interested in this: SAP Screen Personas 3.0 to start beta testing on SAP Kernel 7.22