Is there *always only one right interpretation* of the rhythmic levels? Or is alternate interpretation sometimes possible, i.e. could there be sometimes more "right" answers?

With regular binary structures, there is very little room, if any, for "alternate interpretation." There can sometimes be room for interpreting exactly which level should be labeled as level 0. In some cases, the harmony will seem to be placed at a different level than the melody. In other cases, a melody might meet most of the classic definitions of level 0, yet may have a couple of "holes" where some notes have been displaced from where they would normally occur. Such was the case with our previous "Little Drummer Boy " example. The important thing is to understand Rhythmic Levels and how they relate to one another, and to understand the difference between phrasing and subdivision, even if the precise dividing line between the two is sometimes open to different interpretations.