by Hard Reset
LG Optimus 4G LTE hard resetusing buttons
Turn off the phone.
Press and hold both Volume down + HOME + Search buttons + POWER on your LG Optimus 4G LTE phone.
Factory reset wipe data.
or factory reset via menu
To reset your LG Optimus 4G phone to factory settings and erase all the data on your phone, touch Menu > Settings> Privacy > Factory data reset > Reset phone.
You can use LG Mobile Support tool to repair your LG cell phone, after download select menu Customer Support > Recovery Phone
Before you buy a new cell phone or new tablet, please try the following procedure to repair your device. First charge your battery, backup your important data if possible and in most cases take out SIM and SD card before 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.!