Some people may not like the iOS 9.3 for whatever reason want to go back and install iOS 9.2.1 again, as there are still on time since Apple is signing both iOS 9.3 and iOS 9.2.1, so that if necessary or required, you can proceed to restore an earlier version of iOS.
It should be clear also that this will not be possible here at once, because when Apple verify that iOS 9.3 has not given problems will stop signing iOS 9.2.1, but neither is any disadvantage since iOS 9.2.1 provides no benefit against iOS 9.3, is not even compatible with the jailbreak.
To proceed with the “iOS downgrade” (process by which a version of a pre-installed software is reinstalled), simply download or locate the file or firmware iOS 9.2.1, this file will be similar icon heading this Article and finish in the extension “.ipsw”.
% Appdata% \ Apple Computer \ iTunes \ iPhone Software Updates.
Once the .ipsw file is located/downloaded, it is recommend to your desktop for easy access, to proceed with the iPhone downgrade; connect your device to iTunes using the lightning cable and don’t forget to turn off “Find My iPhone” and while holding down the SHIFT button (the arrow above) click with the mouse on the “Restore iPhone …” button, after this we will open a pop-up that will allow us to find and select the “.ipsw” file previously downloaded or found, must find and click on “Open” once done this iTunes proceed to restore the device to the iOS version selected.
It is important to mention these details, the first is that restoring lose all data stored on our device, and the second is that we can not restore a backup if this has been done with a more modern version, that is, not you can restore a backup if it has been done since iOS 9.3, but if it has made since iOS 9.2.1.