In order to hard reset a Sharp GX15/GZ100, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
Sharp GX15/GZ100 device will be brought back to the default configuration of a brand new device.
1. Heyoo. Start by turning on the phone with the Power button.
2. Enter Menu > Settings > Master Reset > Reset All. Type in your phone's security code (0000 or 0000 by default) and select OK.
3. Lay back and wait for the phone to reset and restart. Done!