No need to go to phone unlocking shop.You can unlock your iPhone5 from home with a help of online unlocking service provider There are several ways to unlock Iphone. According to me remote unlocking is the best way to unlock Iphone.There are many online providers who provide this service .Let me suggest a site where i used to get my Iphone unlocked http://www.simpleunlocking.com/apple/rs16wp8/  If you want you can try them to unlock your iphone 5 and Iphone 3G and you can get free iphone unlock instructions from http://www.mobileunlockguide.com/apple . It's very useful do your step by step unlocking.. Yes it will function properly in US and if you want to install  some applications in your iphone means you need to jailbreak your iphone. To jailbreak your iphone visit essentialjailbreak.com