Some apps are gone and others crash after Samsung Galaxy S2 crash
It sounds like something has corrupted within your phone.

You didn't say if you forced a factory reset - that would be my first suggestion.

Failing that, you're left in a tricky situation.  The only think I can suggest is to root your device and install a new ROM over top, I tend to advise people to install Cyanogenmod.  Luckily there are complete instructions for doing that over at the Cyanogenmod wiki.

Good luck.