Nothing really wrong with them and they will work very often. Remember that we don’t want to exclude them from our playing, but there are times when they will just sound out of place. In one of my coming lessons we will begin switching pentatonic scales as the chords change to begin including other notes.
YES! It’s true.
I hate to be wishy washy, but the definition of “work” is going to vary depending on the ear and style of music. What works in jazz will sound like it’s not working in other styles, and so on. However, a lick does not have to start, end, or even include the note of the chord it is played over. As an example, try playing through the G major pentatonic over a G chord, but leave out the G notes in the scale. Make up a lick with the notes A, B, D, and E. It will sound great! However, you will have more difficulty making it sound like you’re finished, if that makes sense.