Hard Reset SAMSUNG G7102 Galaxy Grand 2

First method:

1. First, turn off the phone by using the Power button.
2. Now press and hold together:  Volume Up + Home + Power button, until you see Samsung logo.
3. Then select from Recovery Mode menu "wipe data / factory reset" using Volume buttons to navigate and Home button to confirm.
   
4. Choose "Yes -- delete all user data" to confirm the whole operation.
5. After that select option "reboot system now".
6. Well done! The hard reset has just been performed.

Second method:

1. Start by turninng on the device.
2. From the Home Screen go to Menu and then to Settings.
3. Tap Privacy or Backup&Reset and then Factory Data Reset.
4. In the next step choose Reset device.
5. To confirm your choice select Erase everything.
6. That's all.

WARNING !
Hard Reset will erase all of your data
All described operations you are doing at your own risk.