In order to hard reset a Lenovo A820, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
Lenovo A820 device will be brought back to the default configuration of a brand new device.
1. First of all, turn off the phone by holding down the Power button.
2. Next, press & hold the Volume Up and Power buttons until a warning appears on screen.
3. You will be asked to select one of these options: Wipe data, Reset Device, clear eMMC.
4. Done! Your phone will now reset and restart, thus completing the hard reset process.