Regarding question 2B:
What exactly is meant? That the centre of the beam will both sub- and superrefract during its propagation?
If so, I think it should be possible as well as for the top and bottom of the beam. If the centre of the beam starts propagating through an unstable airmass (subrefraction) and then hits an overlying inversion and superrefracts.
Regarding the rest of the questions: I agree with Julie.