1st method

  • Go to Settings -> Privacy -> Factory data reset -> Erase everything
  • Insert phone lock code or pattern for verification

 

2nd method

  • Go to dial pad and click *2767*3855#

 

3rd method

  • While holding Volume up (Yellow) + Home Button (Red) press power on (Blue) to power on the phone
  • Release power on and keep pressing the other two buttons
  • With volume up/down go to Wipe data/Factory reset and confirm with the power on
  • With volume up/down go to Yes and confirm with the power
  • Go back to Reboot device and confirm with the power
Samsung Galaxy S2 GT-I9100 Hard Reset
Samsung Galaxy S2 GT-I9100 Hard Reset