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You can try a hard reset, or updating the device's operating system or going back to an older, working system. I will not go into detail about the software side of the repair here, for I am way too ignorant of such matters to guide anyone about them. To find help look your device up on sites like xda developers.
I have come to believe that usually problems that you have caused by meddling with the devices software are only solved by fixing the software.