Noob questions: iPhone 3GS unlocking/jailbreaking
OK, I'm a total noob when it comes to iPhones (aside from what I could pickup in reading some of the stickies). I have experience rooting android phones, but nothing with iOS, so I'm hoping someone can point me in the right direction.
So, my wife has an old 3GS that I am unsure exactly what was done to it in the past, in regards to jailbreaking and unlocking. When it was bought, it was a gift on eBay for a family member overseas, and then was given to her to replace her old flip-phone when the family member got a new phone. Recently, she's been noticing more and more apps that she uses/wants to use need newer versions of iOS (I believe at least iOS5) and want's to upgrade from version 4.2.1, which brings me to my questions. She currently uses the phone on T-mobile (voice/sms only, no data), so I'm assuming that it's jailbroken and subsequently unlocked (either by the seller or her family member), correct?
Secondly, if it is indeed jailbroken and unlocked, from what I've gathered, it could be upgraded via plugging into iTunes, but this would cause her to lose jailbreak and unlock, rendering it at least temporarily unusable for her, correct? I plugged her imei into one of the unlock status checker sites and it came back as locked, which confused me slightly.
If I am correct, what would be the best course of action to get her phone up to date and unlocked to use on T-mobile prepaid? She doesn't use any jailbreak features other than the network unlock, so I don't exactly need to be able to do that.
Thanks for any advice. I had hoped to be able to figure this out on my own, but I kind of feel like I don't entirely know where to start, whatwith it being an old phone/software and not entirely knowing what was done to the phone already.