I installed the kitkitschool apk files to my amazon fire tablet and they seem to work lovely for a short while, but then the device went into reboot mode. In the end I had to reset the tablet back to factory settings to get the fire device to work.
I installed the one billion software and that worked fine on the fire tablet, is still working and my grand-daughter enjoys using it.
I tried loading the kitkitschool APK files on to a Samsung tab 4 device and I can view the videos and books through the app, but the main app is not working correctly. Once the main intro video has finished and I click on the START button the app just throws a little error message, it just not processing any further. My next step is to look through the code in the repo and try work out why the code is not seeing the main library data.
Out of the two apps I believe the kitkitschool software is the better of the two teams. The interface looks better designed and a lot of development time has gone into the programming of the different apps.