Hello Friends!
I am using 3gs, its currently running on ios 4.2.1 and its an jailbreak device (via redsn0w)...
I am using ultrasn0w to use other carrier and i don't have original sim card.
I want to update it to last version of ios which is supported by my device i.e ios 6.1.5
I tried a lot but failed to update.. i use iTunes and original firmware to update my device, even i tried for ios 4.3.4 but failed.
plz help me guyz........................to make update
i wan't untethered jailbreak.........

my device details:
3GS
Version:4.2.1
Model: MC133KH
Serial No.: QR1300XXXXX
baseband: 06.15.00
Operating System: Windows XP S-2
iTunes version: 11.1.3.8

Trying to get my iPhone 6 Plus unlocked went through a company five days ago and still not unlocked trying to go with a diffrent carrier