Objective: To buy iPhone 4 without any contract and used in China (GuangZhou)

Confuses:
I ask several experts and many giving me different answers.
Some say we need to do jailbreak and unlock so that the phone can used in China Telco.
Some say unlock is not necessary, it may compatible with other country.
Some say to unlock the iPhone must perform jailbreak as prior.

Questions:
1) Where can we buy iPhone 4 without any contract?
2) Do we need to jailbreak or unlock the iPhone so that it can used in other China Telco?
3) Can we unlock the iPhone without jailbreak? If yes, how?