Overview
You can remove data from your Android phone or tablet by resetting it to factory settings. Resetting this way is also called "formatting" or performing a "hard reset." The way to do this differs a bit from device to device.
If you can't open your device's Settings app, you can try factory resetting your Android device using its power and volume buttons. We recommend seeing your manufacturer's support site for device-specific instructions.
Warning: Following this process will erase all the data from your device's internal storage, including personal files like photos. Be sure to back up all your phone's data beforehand.
Instructions
Step 1.
Tap System 
Advanced Reset options.
- If you don't see "Advanced," tap Reset options.
Step 2.
Tap Erase all data (factory reset) Reset phone or Reset tablet. If needed, enter your PIN, pattern, or password.
Step 3.
To erase all data from your device's internal storage, tap Erase everything.
Step 4.
When your device has finished erasing, pick the option to restart.
Step 5.
Set up your device and restore your backed-up data.