Buy an iphone with contract in uk and use it in india?

I have a friend in uk, is it possible that he buys an iphone with a contract at subsidised price in uk and i use it in india after unlocking it? What are the problems should i face to use dis phone and how i should resolve these problems?

Yea, you just have to make sure it's unlocked already if you are planning to purchase another SIM card in India or have global/international roaming enabled by your service providers.

About the bands: All Iphone models are quadbands. No need to check on that

This is basically no problem as all carriers in the UK are GSM, so once unlocked their devices will work with all GSM carriers in India as well. If you get a proper factory unlock for the device, it will even stay after upgrading iOS.