Signal to noise ratio here is, as said elsewhere, dreadful. Could the amateurs and non pilots (please see the title of this forum) please keep their musings to themselves? Incoherent ramblings by spectators aren't helpful or useful.
Facts seem to be;
Whatever occurred could have occurred or started to occur anytime during the 40 something minutes after the last communication during which the a/c flew on normally and perhaps continued to occur all the way to the sea.
It is perfectly normal not to talk to an a/c for that length of time if remaining on its cleared route. Why on earth not? Pilots and ATC tend not to jabber pointlessly, unlike some here.
Comms were not established as the FIR boundary approached. Loss of comms in that area is, as previously stated not unusual due to extreme range. For those with no imagination at all had a mayday been made than all other aircraft within c. 200 miles would have heard it even if ATC didn't. Ergo none was made.
40 sec later the a/c began to descend rapidly and entered a series of turns. This is not inconsistent with the drill for rapid depressurisation/rapid descent though the 360' turn is not usually included in that. The 90' turn however most definitely is used in some companies's drills. The decisive turn off airway and immediate rapid descant is a well known and unique signature.
The fact that these events occurred almost immediately upon entering Egyptian airspace may or may not be a coincidence.
The turns are confidently reported as 90' left followed by 360' right. These numbers are precise parts of a whole turn and therefore do not look like the random gyrations of an out of control aeroplane. It seems most likely/almost certain that the aircraft was under a good measure of control at this point. Using these manoeuvres to speculate or infer damaged controls is simply not logical and beyond what the evidence supports. (not saying it's impossible, just there is no evidence to support it). It is, however, vanishingly unlikely for those turns to be random. It seems we can assume reasonable lateral control at least at this point.
"Spin". Oh dear. A spin is a manoeuvre where the a/c rotates almost about it's wingtip. It also only occurs at stall speed (except certain high g cases which an Airbus is most unlikely to ever reach). That loss of speed has not been reported. Bar an Extra at an airshow no aircraft - let alone an airliner does just one 360' spin, let alone a quarter one way and then a single turn the other. Airbi don't/can't spin in any but the most unusual circumstances, the flight control laws just won't allow it. If one did I'm pretty sure it would have to be in direct law (how did it get there?) and would almost cetainly be totally unrecoverable by any normal pilot and therefore result in multiple spins all the way down. Damage sufficient to cause a spin would have to be huge and catastrophic (loss of a large proportion of a flying surface or possibly t/r activation is about all I can think of) and most unlikely to result in a single turn - all but impossible. No radar will identify a spin at the 100+ mile ranges we're talking about - as the aircraft is effectively going vertically downwards the spin had no or virtually no "width" for radar to see. Compare with a 360' turn which requires two - four mies at any flying speed. Forget spin. A 360' turn was reported as observed and we have to go with that for now.
The separation interval between the left and right turns would be helpful. Were they contiguous or separated and distinct manoeuvres?
Timescale between leaving FL370 and loss of radar return at FL150(?) would be helpful.
We don't seem to know much more. No doubt we soon will.