Hard Reset (Factory Reset)
If you forget your lock sequence and backup PIN, you will have to perform a hard reset to gain access to your phone.
Performing a hard reset deletes all of your user data, which includes pictures, videos, and music saved to your internal memory. Please make sure to back up your information prior to performing a hard reset.
Turn the phone off.
Press and hold the following keys at the same time: Volume Down Key
+ Power/Lock Key 
on the back of the phone.Release the Power/Lock Key
only when the LG logo is displayed,
then immediately press and hold the Power/Lock Key again.Release all keys when the Factory hard reset screen is displayed.
Press the Power/Lock Key
to continue or either of the Volume Keys 
to cancel.Press the Power/Lock Key
once more to confirm or either
of the Volume Keys to cancel.