TPToolbox : http://forum.xda-developers.com/showthread.php?t=2756314


4.4.4 : http://forum.xda-developers.com/showthread.php?t=2712680
http://forum.xda-developers.com/showpost.php?p=42505399&postcount=2


complete android 9 guide : https://forum.xda-developers.com/hp-touchpad/help/how-to-install-android-7-x-hp-touchpad-t3512182