ios 4.2.1 custom firmware without bb update

If you are an unlocker and know about 06.15.00 unlock method with ultrasn0w 1.2 , there is a simple way to update to iOS 4.2.1 without basebande update with pwnage tool 4.1.3 . easy unlock and jailbreak But its need you have 05.13.04 bb or below.
Tools needed

1 . Custom firmware for iphone 3Gs / 3G  4.2.1

    Download custom firmware iPhone 3Gs
    Download custom firmware iPhone 3G  

2. Download Redsn0w 0.9.6b

3. Download Apple original firmware

    Download original firmware iPhone 3GS
    Download original firmware iPhone 3G

Guide :

1. Connect your phone with PC and switch off

2. Open redsn0w and choose Original firmware.

3. If you have newboot just press “yes”

4. now click “Next”

5. Choose “Just Enter pwned DFU mode right now”

6- now click “Next” again “Next” and follow the screen.

* you can useb iReb for pwned DFU mode too.

After that open itunes and press “Shift + Restore” and choose custom firmware 4.2.1

it will finish very quickly

Once you update you firmware

1. Connect your phone with PC and switch off

2. Open redsnow and choose Original firmware

3. If you have newboot just press “yes”

4. now click “Next”

5. Choose Only “Install Cydia”

6. now click “Next” again “Next” and follow the screen.

If you r getting White Cydia Icon just switch of your phone and open redsnow choose Stock firmware 4.2.1 and choose the option “Just boot tethered right now” and click “next” again “next” then follow the screen then you will see the cydia.

Finally you can see your phones is with your old Baseband. now just you can install the ultrasn0w 1.2 from Cydia