Another interesting thing that this photo shows is that condensation is very quick to form (fractions of a second, at most), AND it is also very quick to dissipate. So to answer the OP's question, even if a jet momentarily punched a visible hole through a cloud, it is quite possible that that hole would nearly instantly close up again once the jet has passed.

It doesn't make sense that that rocket was supersonic (one wouldn't see shocks so far in front, nor so numerous, I would think; also the waves are concentric round rings, they do not look like not conical or curved bow shocks). I think it is more likely that the rocket was going at a very high subsonic Mach number when that photo was taken. It's hard to tell the scale but if ring 1 was 50m in front and ring 11 was 120m in front, that would suggest that ring 11 was emitted about a quarter of a second before ring 1 was...?

Heat transfer to the surroundings while falling is the biggie; will be a combination of water-air temperature difference and also evaporative cooling (a function of relative humidity).

correct approach.

+1 for the recommendation of Stick and Rudder, it's one of the best books I've ever read for this sort of question.

not a very good example because air drag is not neglectable. In practice (i.e. with drag) a high powered rifle bullet will reach about 10,000 feet. But if you neglect drag, you would calculate a 2700ft/sec (823m/s) bullet to reach over 100,000 feet. Actually let me have another go at it - this is actually a VERY good example of learning where it is OK to neglect air drag and where it is not.

Why the downvote? Everything here looks correct to me...!