Changing instrument and tuning
When you change the instrument or the tuning in the settings, it affects all the features like chords, scales, arpeggio, tuner or circle of fifths. But it does not affect all features. Some features like the songbook, chord progression or the fretboard trainer do store the tuning when the item is created. This means that you have the same tuning with the same chords and fingerings in a song, every time you open it. But you can change the tuning/instrument for a song or chord progression in the menu. Then the fingerings are changed too and the new tuning is stored in the item.
The fretboard trainer is different. You cannot change the tuning/instrument of a quiz. If you want to learn a new tuning/instrument, you have to create a new quiz.