[icosa]

Re #2, keys, scales, and chords are fundamental units of Western music. You could compare them to words, which are joined into sentences. Chord progressions are sequences of chords, which only make sense in the context of the current key and scale.

Learning about keys, scales, and chords will help you understand music but not necessarily force you into predetermined patterns. Learning chord progressions will help you hear patterns in music, which may reduce your enjoyment of pop music since a handful of progressions are used almost everywhere. On the other hand, if you enjoy trope-spotting, it may increase your enjoyment.