Hard Reset LENOVO S820

First method:

Turn off the phone by holding the Power button.
In the next step press and hold the Volume Down and Volume Up key for a short while.
While holding these keys press the Power button.
Release Volume keys when you see an Android image on your screen and then release Power button.
Press Volume Down to choose "wipe data/factory reset", and then push the Power button to confirm.
Select "Yes--delete all user data". Use Volume Down button to scroll and Power key to select.
To restart the phone, select "reboot system now".
Success! The hard reset is done!