How to Jailbreak iPhone 4 on iOS 4.2.10 Untethered?

Hello Drick, yes, downgrading your iPhone 4 back to iOS 4.2.8, iOS 4.2.7, or iOS 4.2.6 is the only possible way available in order to get untethered jailbreak. However, you should be noted that downgrading will require you to have saved SHSH blobs. If you don’t have saved SHSH blobs, then this process is impossible.

Anyway, if you have jailbroken your iPhone 4 before, there are possibility that Cydia might have automatically saved the SHSH blobs of your device. To check if you have saved SHSH blobs, all you need to do is launch TinyUmbrella, then connect your iPhone 4 via USB cable, and then select your device form the list of iOS devices. Then under the under Advanced option, choose Request SHSH from Cydia option and then hit the Save SHSH button. Just carefully watch via the log tab to see what you get. The rest of the tutorial on how to downgrade can be found here. Once you have completely downgraded your iPhone back to iOS 4.2.8 you can now jailbreak it with JailbreakMe 3.0 or with Redsn0w 0.9.6RC16.

If you don’t have saved SHSH blobs, then the only way to jailbreak your iPhone is through Redsn0w 0.9.8b4.The step by step guide on how to jailbreak iPhone 4 on iOS 4.2.10 or iOS 4.3.5 can be found here.