Hi all, I am looking to buy a used 3GS from local sellers. What exactly do I need to ask of the seller to ensure both jailbreakability AND unlockability (im on T-Mobile) Thanks!

asks,
what version of firmware and base band?

have the device jail-broken b4? if yes, did the seller save the shsh signature on Cydia or locally?

and of course ... device's cosmetic conditions is a plus!

lol

Originally Posted by zragnarok

Hi all, I am looking to buy a used 3GS from local sellers. What exactly do I need to ask of the seller to ensure both jailbreakability AND unlockability (im on T-Mobile) Thanks!

You need to confirm the OS version and the mobile firmware (also known as baseband). These things can be checked with TinyUmbrella - even if the iPhone is not currently activated. The Firmware Umbrella

TinyUmbrella can also be used via manual mode to check if there are saved SHSH for the iPhone. TinyUmbrella asks for an admin password the first time it's launched, but you really don't need to enter this if you don't want to restore on that particular machine.

Don't trust the seller on this, ask if they can run this tinyUmbrella and confirm for you. The tool makes zero changes to the iPhone.

For a 3GS you need:

OS:
3.1.3 to 4.0.1 (plus a way to bypass the slide to unlock - either a SIM card from the carrier that the iPhone is locked to or one of these 'universal / phonebook sim cards')
3.1.2 or lower (ideal, they don't require any special SIM card)

Modem Firmware
OK - 5.13.04, 5.12.01, 5.11.07, 4.26.08 or any 1.x.x or 2.x.x firmware
BAD - 5.14.02 or higher.

Be careful, some people will try and sell you an iPhone running 4.0.1 but with 5.14.02 modem firmware, this means that they have upgraded to 4.1 and then downgraded again - but it is impossible to downgrade the modem firmware.