I am posting a guide to upgrade/downgrade to any newer/older versions of Android (if present).
Currently Supported Phones:
PM me if you want your phone to be supported.
(2) Download LG UP from here.
(3) Download the required files from here.
(5) Create a new folder inside the "model" folder.
"8916" (K420DS & K420N)
"8909" (MS428 & K425)
(without the double quotes)
(7) Run the ".reg" file which is provided in the zip file. Select "Yes" if you see a prompt and then select "Ok".
(8) Put your phone in download mode and connect it to your computer using USB.
(8) Open LG UP application in admin mode.
(9) Select the "Upgrade" option. Click in the blank space under "File Path". You will see three dots. Click on it. Select the KDZ file for your phone.
(10) Close LG UP.
(11) Open LG UP again in admin mode. Choose "Refurbish" option (if you want to completely wipe your data) or "Upgrade" option (if you don't want to completely wipe your data) . Select "Start". LG UP will start flashing your phone.
*** Don't disconnect your phone until the progress bar shows 100% ***
You have successfully flashed the KDZ.