To reset an LG phone to default factory settings, access the test screen by turning off the phone, and select the Factory Reset option. Once the Android Recovery screen appears, select the Wipe Data or Factory Reset option, depending on the model.
To access the test screen on the LG G2 model or a newer version, turn off the phone by pressing the Power button and selecting the Power Off option. Press and hold the Home and Volume Down buttons, then press the Power button. After 15 to 20 seconds, the test screen with the LG logo should appear. Select the Wipe Data or Factory Reset option by using the Volume Down key to navigate to it, and press the Menu button to select it.
If a confirmation screen pops up, use the Volume Down key to highlight the Yes option, and press the Menu button. Once the Reboot System Now option appears, select it, and wait a couple of minutes for the process to complete. In some cases, pressing and holding down the Home, Volume Down and Power keys immediately initiates the restart sequence. If this happens, select your desired language, and complete the setup process by following the steps identical to the ones during the initial setup. This process erases all personal data except the information stored on an SD or SIM card, so create a backup beforehand if necessary.