I'm thinking about purchasing a Sprint Galaxy s4 (what can I say, it's purple). However my provider is AT&T. If the owner gets it unlocked, is it compatible with use on AT&T? I'm thinking I could flash an AT&T ROM on it, but if I can't do that without bricking it, maybe I can still use it stock and rooted. If I use this on AT&T are there any features I might lose, for instance LTE? Thanks for any help on this.