Unlocked iPhone 4 users are being told not to update to iOS 4.2.1 to protect their device to become locked. But thanks to TinyUmbrella as it allows you to upgrade to iOS 4.2.1 without baseband upgrade. After upgrading to iOS 4.2.1 you can jailbreak it using the new version of Greenpois0n 4.2.1 RC5.
Remember that you can only unlock your iPhone 4 on the older 1.59.00 baseband. If you are already on some new iPhone 4 baseband then you will not be able to unlock your iPhone 4 device.
You can check your baseband version by going to Settings > General > About > Modem Firmware.
Follow the below STEP BY STEP HOW TO GUIDE for upgrading to iOS 4.2.1 without upgrading baseband (only for older baseband users)
Chronic Dev Team has just released the GreenPois0n RC5 untethered jailbreak for iOS 4.2.1 on iPhone 4, 3GS, iPod touch 4G, 3G and iPad. TinyUmbrella is just updated for iPhone 4 ONLY.
STEP BY STEP HOW TO GUIDE TO USE TinyUmbrella to Upgrade to iOS 4.2.1 on iPhone 4 while Preserving Baseband
- Download and install the new version of TinyUmbrella
- Download iOS 4.2.1
- Launch TinyUmbrella and Start TSS Server.
- Launch iTunes
- Plug-in your iPhone 4 device.
- Restore or Upgrade to the iOS 4.2.1
- If you get an Error 1013. Take a chill pill. There is nothing to worry about.
- Now put your iPhone 4 in the DFU mode.
- Download GreenPois0n RC5 to jailbreak your iPhone 4 device.
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