i sold my iphone 4s to a pawn shop and got a iphone 5 from my friend, it won't respond at all, even when plug into itunes

You can NOT get help here.

Sounds like you need to be a little more selective in who you consider to be a "friend".

Unauthorized modification of iOS has been a major source of instability, disruption of services, and other issues

This is why.

By the way, the next time someone offers to sell you something for less that 20% of what it would cost to buy it in the store, run.

to remove the jailbreak you can do this by updating the firm ware of the phone and that should reset it to proper factory settings and the jail break is gone or restore that phone by using restore from back up in itunes.

I'm sure responding to a post 14 months old is really helpful to the original poster.