You can hard reset your LG Optimus L7 P700 to restore the factory default settings. Caution: If you perform a hard reset, all user applications and user data will be deleted. This cannot be reversed. Remember to back up any important data before performing a hard reset.
Switched off your phone then press and hold the Volume down key + Power key with your left hand.
When the LED on the bottom of the phone lights up, touch and hold the Menu key with your right hand. You need to do this immediately, before the screen displays the LG logo. Make sure your left hand is still holding the Volume down and Power keys. Then release the power key at vibration time.
When the LG logo is displayed on the screen, continue to hold the keys for
around 2 seconds, and then release all them at the same time, before the LG
logo disappears. Leave your phone for at least a minute while the hard reset is carried out. You will then be able to switch your phone back on.