Unlocking iPhone 4 help

I recently purchased a O2 locked iphone 4 (from uk) and i was searching warez and i saw a guide on how to jailbreak and then unlock iphone on iOS 4.0. I was wondering if after unlocking it on the iOS 4.0 if i was to upgrade to a more recent one like 5.01 would it still be unlocked? and if it is does it still have to be jailbroken on the iOS5.0 for the unlock to work (can it not be jailbroken but still fully unlocked? If so then when/if i choose to resell my iphone 4 will it stay unlocked for the next user? ( so essential I’ve payed £40 less for a just O2 locked (instead of universal unlock) phone that can be easily permanently unlocked universal?)
Answer #1
First off all you need to tell me (us) what is your current firmware (FW) and baseband (Modem Firmware = BB)? Remember one thing, it’s not important what firmware version you have, it’s important what BB (baseband) you have (BB is related to unlocking, FW to jailbreaking).
After that you will get instructions what to do…
You have 2 options.. either to unlock it using ultrasn0w (software unlock) or GEVEY (Micro chip). Ultrasn0w ONLY support 01.59.00 BB and GEVEY support all other except 2 latest BBs and that is 04.11.08 and 04.12.01
ATM every FW can be jailbroken, ONLY last one (5.1) has TETHERED JB (not untethered)