The Fonepad K004 simply lacks the hardware capabilities to run modern Android versions smoothly. With only 1GB of RAM and a decade-old single-core Intel Atom processor, attempting to port Android 7.0 or higher would likely result in an unusable device.
To ensure a smooth experience with your custom ROM: asus fonepad k004 custom rom 2021
Enable on your Fonepad via Settings > Developer Options . (If hidden, tap Settings > About Tablet > Build Number seven times). The Fonepad K004 simply lacks the hardware capabilities
Connect your tablet to the computer while still inside the custom recovery menu. Your PC should recognize the tablet as an external storage drive. (If hidden, tap Settings > About Tablet >
Asus Fonepad K004 Custom ROM Guide: Reviving Your Classic Tablet
(Optional) If your chosen ROM does not include Google services, download a compatible "OpenGApps" package (Select and the matching Android version), then flash it immediately after the ROM file.