In order to hard reset a Sharp GX20, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
Sharp GX20 device will be brought back to the default configuration of a brand new device.
1. Press & hold the Power button until the phone turns on.
2. Now press Menu button. Select Settings > Master Reset > Reset All. Enter your security code, which by default is 0000 or 000000, and confirm with OK.
3. Wait until the phone resets and restarts. Complete.