can i be a full time student if i take online clas

You won't have more time

Yes, you can take enough online classes to be full time (that's like 4, 3 hour classes) But it's a little harder to get into online classes, and they do require work. Also, it might be hard to find online classes for your major depending on your major. I think taking on campus classes is the best idea, you might even have sisters in your classes. Your first semester on campus is going to be pretty hectic anyways.

It will be considerably harder. You will find yourself only on campus for mandatory sorority events. Which means you will be removed from your pledge class. Having classes with sisters is awesome and you can also meet other great people in classes and hanging around. Also you'll be missing out on a lot! What is your reasoning for wanting to do it this way? Also online classes take ALOT of time as you can't just ask a question right away or form study groups as east. Also living in the dorms your first year is the best experience you'll love to hate.

Also what I'd you get released from rush?

stick to on campus imo