Prerequisites to downgrade Lollipop to KitKat:
- Create a backup of your device – MUST to-do step!
- Make sure USB Debugging is enabled on your Nexus. You can enable from Settings > Developer Options > toggle USB Debugging on.
- If you don’t see the Developer Option, go to About Phone and tap Build Number multiple times until you see the notification pop up.
- Your Nexus should be charged up to at least 70%.
- Your Nexus should have an unlocked bootloader.
How to downgrade Lollipop to KiKat:
- Download the factory image for your Nexus from here. Download ADB Tools on your PC. Move the factory image file into ADB Tools folder and extract it.
- Turn your Nexus off and enter into Flash boot mode: press and hold Power and the Volume Down keys to enter.If you have a custom recovery installed, use the Volume buttons to engage Recovery Mode and press the Power button to confirm.
- In case of stock recovery, push the Power key followed by Volume Up button to when see the Android bot. Once in the Recovery Mode, you will be efficient to navigate with the Volume buttons and confirm with the Power key.
- Once in the recovery, clear cache by scrolling down to wipe cache partition.
- Also wipe data / factory reset; use Power key to confirm.
- Next, connect your Nexus to your PC with a USB cable.
- Open the ADB Tools folder. Locate the flash-all.bat file and double-click it.
- The process will start now which will reboot your Nexus once it has been flashed with downgraded Android version.
- Once you see the Nexus getting back up, setup the device like you usually do and ta da!