Jailbreaking & unlocking old iPhone

[Antonioium]

So my girlfriend has an old iPhone 4 on ios 4.0.2 and she's giving it to me. It doesn't have any service either. It's from at&t and I'd like to eventually end up with an ios 6.1.2 untethered, unlocked iPhone using T-Mobile. I know I'm going to have to unlock it and put the sim card in, but from what I've read you need to have service to use evasi0ns exploit to jailbreak. Is this right? Is it possible? What steps would I need to take to end up what what I'm looking for? Keep in mind I'm an android user and never really used iPhone or iTunes before. Thanks a lot for your time and advice in advance.

 

[2k1]

Gonna need to make sure ya have the blobs got that firmware first thing if not ya can't go to that firmware.

 

[Antonioium]

So I take it there's no way to go to a firmware other than the latest? To get blobs I need it to be jailbroken to begin with right? Currently it is not.

 

[urstrinath]

Yeah start with jailbroken

 

[Laelipoo]

If she never saved the shsh through tiny umbrella, you cannot do what you're looking to do here. Sorry.