Can The AT&T iPhone Be Used With Virgin Mobile?

Hi. I bought an AT&T iPhone 4s (from eBay) and I've been trying to activate it with Go Phone but I haven't been able to, so I was wondering if I could activate it with VirginMobile or do I need to buy a Virgin Mobile iPhone?

I have 3 other questions about Factory Locked iPhone 4s:

How do you know if 'your' iPhone is unlocked? How do you unlock an iPhone 4s for free? And Finally, will I lose everything like my pictures, videos, contacts Ect. When I unlock it?

Att iphone will not work with virgin mobile.