Help Me Frn

  1. mohit143
    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 make update
    i wan't untethered jailbreak.........

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