Hard reset LG Optimus  Pro C660 full reset

Use Hard Reset to initialise your phone.
When the phone is turned off, Press and hold Home key + Volume down key + Power key for over 10 seconds. When screen
shows LG logo, release power key.
After screen shows hard reset screen, release other keys.
Leave you phone over a minute while it performs hard reset, then your phone will be turned on.
Caution: If you perform a Hard reset, all user applications and user data are deleted. This cannot be reversed. Remember to back
up any important data before performing a LG C660 MFL67300803 hard reset.

LG Optimus Pro C660 hard reset

General advice: Before you buy a new cell phone or new tablet, please try the following procedure to repair your device in a software way. First charge your battery, backup your important data if possible and in most cases take out SIM and SD card before doing factory reset. It is impossible to recover your data after doing a hard reset, so online backup is always important. For all of your data, a backup should be done on an external device, hard drive, raid system or media. With or without insurance, if your cell phone lost, damaged or stolen at least your invaluable data is backed up in a safe place. If you are about to sell your phone and you want to wipe your personal data, or if your phone affected with virus you have to do a hard reset. In some cases, you can delete the forgotten password or lock pattern from your device as well. All information is for devices with stock based ROMs. If you are using rooted device, always back up your EFS folder first, containing your IMEI info, etc.! Please also note, that a hard reset operation will not unlock your mobile phone's SIM lock or network lock, but it will remove the unlock pattern, remove the user password or PIN password (NOT the SIM card's 4 digit PIN code). Also note that the firmware version will not be affected in any way, it will not be downgraded, it will remain the same you are using and if you have rooted your device, root privileges remain also unaffected.