I jailbroke my iPhone 4 iOS 7.0.4 (11B554a) with evasi0n 7. And that's the worse I did with my phone. I am new to iPhone and was just curious about jailbreaking. But that jailbreak corrupted many of my apps including iOS own apps.
I am very very happy with iPhone in its default iOS. I want to restore back to 7.0.4.
P.S: I tried "Erase all data and settings restore" from iPhone settings but the process stucks at spinning wheel after restart.
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Update::
Ok. I did that. I downloaded ipsw of iOS 7.0.4 and tried to install it through shift+restore method through iTunes. But it keeps giving me error 21 again and again. And don't know about it.
Best Answer
Attempting to reset your jailbroken phone from your phone will break everything. You'll need to put your device in DFU mode and restore it with iTunes. Connect your device to iTunes, then hold the power and home button until the Apple logo shows, then keep holding home and let go of power. iTunes should prompt you to restore iOS.