1. Phone is not under anybody's name. Only the plan is.

2. He will be subject to penalty for early termination of contract. Since he is the one enjoyed the rebate from the plan, he should bear the penalty. Should not affect your price at all. Your new phone price is considered to be RM2490 (16gb) and RM2990 (32gb). The price he sells you should be based on those price less discount due to second hand.

3. Yes, possible to jail break. You can restore back to original by updated your software with iTunes and no way to tell that it's been jailbroken before. Once you restore, you can send back to Maxis for warranty claim (if necessary).

4. You NEVER need to go to Maxis for update. You only need to go to Maxis for warranty claim. You update software through iTunes as per normal.