unlocking an iphone to be used outside the country

[mic712]

I was planning to get an iphone for a friend outside the U.S. I have already bought a used iphone and I was going to jailbreak it using redsnow and then unlock it using ultrasnow. But after doing some research, mostly on youtube I have become a little confused. I dont understand very well which iphone firmwares can be jailbroken and unlocked and how to do so without the unlock doing tethered.