on the dial pad; this will automatically restart and wipe the device. Official Support

When you flash (reinstall) this file, you restore the phone to its factory state, fixing any software corruption.

Open the Flash Loader tool. Click the button to select the configuration files from your extracted firmware folder (usually labeled with extensions like .dff or .tfs).

: Refreshing a corrupted operating system to factory-fresh performance. Essential Tools for Flashing