How to restore iOS 7.1.1 and downgrade iOS 8 beta 2 on iPhone, iPod or iPad have been a problem after the iOS 8 has been reported to be more unstable than the first beta. Due to the instability and bugs of the iOS 8 beta, some non-developers who downloaded the software wish to return to the earlier firmware.
How to Restore iOS 7.1.1 and Downgrade iOS 8 Beta 2
1 - Make sure to back up all your important files before restoring or downgrading software because the process automatically sets the device to factory settings mode. Basically, unless you back up your files, any third party apps, emails, contacts, messages and music will be lost.
2 - Download the proper ISPW here > save to the computer desktop. You will not be able to downgrade to earlier versions of iOS because the only public firmware that Apple is signing is the iOS 7.1.1. If your device is jailbroken, there is no way to downgrade it.
3 - After downloading the firmware > plug your device into the computer > launch iTunes > Check for an update or Restore iPhone.
For Mac users, while in iTunes > hold down alt or option key > click on Check for an update > look for the ISPW and open the file > update.
For Windows users, while in iTunes > hold down the shift key and left click on Check for an update > update.
Once the software starts updating, do not turn off or unplug your device, as such make sure that you have sufficient battery before starting the process. The device will turn off and on, and you will need to enter your passcode if you have one. Afterwards, the device will show one last screen to finish the update and then, you should be back to iOS 7.1.1.
For first time beta users, it is a must to keep an eye to the expiration dates of the iOS 8 betas. If you have not downgraded to iOS 7.1.1 or updated to the next beta and the expiration date arrives, your device will enter recovery mode, which means that it will no longer be usable.