My MacBook Pro, gets stuck at boot screen and the graphics look weird
Unfortunately you may have hardware issues if yours is an "Early 2011" model, many owners have reported symptoms similar to yours with the culprit being failed ball grid array solder on the graphics processor. There's some info here. The article has a link for a utility that will allow you run solely on the integrated Intel HD3000 graphics so at least you'll be able to continue using your MacBook (in theory at least, we do have an Early 2011 i7 15" on campus but so far it's not had any problems).

Ultimately the fix will either be a replacement logic board or you can try any one of a number of companies offering to "re-ball" or "re-flow" the solder on GPUs. Any company offering Xbox 360 or PS3 repairs should be able to do this. 

Here is a link to the "MacBook Pro Repair Extension Program for Video Issues" for your Mac model.