How to unlock a iphone 4 to work anywhere in the world?

Is it possible to unlocked or jailbreak iphone 4 for free is there such a site

ITUNES. I don't know

I too had the same situation few days ago. I was searching a free unlocking solution for my sister's iPhone 4. But i couldn't find anything reliable. If you need to unlock your iPhone 4 safer, You need to spend something for it.
I unlocked my sister's iPhone 4 using remote unlocking service. This method of unlocking was safe, simple, affordable and quick. I got the remote unlocking service from http://www.mobileunlocksolutions.com/apple-iphone-4/rs16wp9/ at affordable cost with easy unlocking instructions. This method of unlocking didn't require a jailbreak too. You too can have a try with this unlocking method if you wish.

Unlock would depend on the baseband of the iPhone. Don't think you'd be able to do it for free anymore.http://chronicunlocks.com can though. I got an iPhone 4 unlocked through them, worked out fine.