LG K20 hard reset using key combination
How to unlock LG K20 forgotten password, remove knock code

If your phone does not restore to its original condition, use a Hard Reset (Factory Reset) to initialize it.
1 Turn the power off.
2 Press and hold the Power/Lock key + Volume Down key on the back of the phone.
3 Release the Power/Lock Key only when the LG logo is displayed, then immediately press and hold the Power/Lock Key again.
4 Release all keys when the Factory hard reset screen is displayed.
It will ask "Erase all user data & restore default settings?"
5 Press the select Yes to start using the Volume Key.
6 Press the Power/Lock Key once more to confirm.
The phone will reboot and reset itself.

If you perform a Hard Reset, all user applications, user data and DRM licenses will be deleted. Please remember to backup any important data on local media or in the cloud before performing a Hard Reset.
All of the phone's contents, including content which you create or download, will be deleted after a Factory Reset.

Another possible Recovery Solution for LG K20

Power Reset The phone is locked-up and does not function. How can I reset it? In the case of a malfunction or lock up error, press and hold the Power/Lock key  (on the back of the phone) for 8 seconds to reset the phone.

Backup & reset
Allows you to copy data from a previous device to a new device. You can also back up data or restore data from a previous back up.

GOOGLE BACKUP & RESTORE Back up my data 
Enable this option to automatically backup your data to Google servers (cloud)

RESET Factory data reset  Allows you to erase all of the data on the phone. Read the warning, then tap RESET PHONE . Tap Delete all  to confirm and reset the phone. Reset settings  Allows you to restore the default system settings.

Anti-Theft Guide
You can set up your device to prevent other people from using it if it’s been reset to factory settings without your permission. For example, if your device is lost, stolen, or wiped, only someone with your Google account or screen lock information can use the device.

Set a screen lock : If your device is lost or stolen but you have a screen lock set, the device can’t be erased using the Settings menu unless your screen is unlocked.
Add your Google account on your device : If your device is wiped but you have your Google account on it, the device can’t finish the setup process until your Google account information is entered again.
After your device is protected, you’ll need to either unlock your screen or enter your Google account password if you need to do a factory reset. This ensures that you or someone you trust is doing the reset.  NOTE Do not forget your Google account and password you had added to your device prior to performing a factory reset. If you can't provide the account information during the setup process, you won't be able to use the device at all after performing the factory reset.

After 5 unsuccessful attempts to unlock your phone, you're prompted to enter a text phrase to confirm that you're trying to unlock your phone, unless you've set a Knock Code. After 6 unsuccessful Knock Code attempts, you're prompted to enter your Backup PIN to unlock your phone. If you've set a Knock Code, after 6 unsuccessful attempts, you're prompted to enter your Backup PIN to unlock your phone. You have 10 opportunities to enter your unlock sequence. After 10 unsuccessful attempts, your phone will automatically perform a factory data reset and all of your personal files will be erased. You will be warned after the 9th unsuccessful attempt.

LG K20 hard reset from the menu

Factory data reset – Reset your settings to the factory default values and delete all your data. If you reset the phone this way, you are prompted to re-enter the same information as when you first started your Android phone.

Go to Settings > Backup & reset > Factory data reset  and confirm
Enter your unlock sequence if you have configured one, then tap Delete all and OK to confirm
All data will be deleted!
Check the software version on your mobile phone: Settings > About phone > System updates > Check now.

NOTE: Your personal data from internal phone storage — including information about your Google account and any other accounts, your system/application data and settings, any downloaded applications and your DRM licence — might be lost in the process of updating your phone's software. Therefore, it is always recommended to backup your personal data before updating your phone's software.

LG K20 Update Firmware

This option allows you to download and update the Firmware for your device.
1. Tap Menu > Settings > System updates > Update Firmware . 2. Follow the on - screen instruction

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.