Android Apps for Guitar Music Theory

I have installed many android apps for guitar music theory or basic scales, pentatonic / Circle of fifths apps. Also began looking at Tabs / Notation, song lyrics and tabs, etc.

The short answer is. Some do what the apps say.
Others of the android apps do not go the distance in expressing the intended goal of the app.
Still, each one has virtue of some sort even if it was not the Android App Authors vision.