1. does the melody note always have to be in the soprano line?
Always have to? Well, mostly. You could mix things up and play the melody lower and strum chords over it, for example. Remember, jazz is about freedom. You think about that.
2. Are most Chord Solos made with drop 2 voicings?
Most? I'd have to stop and count, but that's not the way to think about it. Play the chords that work and don't worry about their classification.
3. Do you have to change chords everytime a melody note changes?
Have to? No.
Did you go to a military school or something?
My advice is to listen to some CM guitar playing on Utube. It will answer all your questions and more.