What is RUU?
RUU is a one short restore file with stipulations. But unlike the ROM you don’t need to have Custom Recovery installed on your phone to use the RUU file. But you do need to have Locked Bootloader to use this file. Here is how to use the RUU file:
> Download the RUU.exe file for your device; click the file twice to open it on your Computer.
> Go to the RUU panel.
> Connect your phone to your computer.
> After you see the instruction, click next.
> Follow the on screen instruction.
> After RUU verifies your phone it will tell you all about the devise you are using.
> This will also tell you about the version you will get after the update.
> It will take approximately 10 minutes.
> After RUU is completely installed on your phone, disconnect the phone from your Computer.
> The newest Android is now running in your phone.
Technobezz Explains RUU
Performing RUU on your phone is optional. Only if your phone is not functioning properly you need to run the RUU file, otherwise it may harm your device. So think about these problems before running the RUU file
> Back up all your files.
> Make sure your phone battery is at least at 30 % when you are doing this.
If you can update your phone via OTA then don’t stay away from using RUU.