I still stand by what I said 4 days ago way back on page 12, namely that some internal force at the rear aircraft caused the rupturing of the pressure vessel which led to the tail detaching via an almost clean break around the frame just forward of the empennage.
Further theorising, the "bomb" also penetrated the aft pressure bulkhead causing the APU cone to detach along with the HS. Picture below shows tearing outwards of the aircraft skin at places, suggesting a rough location of the "explosive" force, with the skin then tearing linearly along a natural line, namely the frame.
So, in true Pprune internet expert form, I surmise: "explosive" device in aft seat row, aft toilet or rear galley. Detonates at top climb. APB breached, APU cone and HS detached by pressure shockwave and fall away. At the same time, the fuselage forward of the VS is ruptured and splits along the frame. Tail section detaches and falls away. Little/no fire damage as separation is caused by shockwave and shrapnel and occurs before any significant heat damage can occur. Seat of the explosion/fire remains with main fuselage. The rest of the aircraft continues forward accompanied by significant pitching down motion. 1 or both engines rotate up and over the wings, off their pylons due the pitching moment. Ruptured fuel lines etc lead to start of fireball. Remainder of aircraft falls, inverted, and lands planform and generally intact (wings and associated fuselage) further along the path of flight.
Red arrows show skin ruptured outwards. The blue arrows show crush and tears caused by impact with the ground at terminal velocity.
Note in the second picture the large piece of torn back skin near window followed by the skin "unzipping" itself up and over the roof and along the rivet line to the right. The strip of missing paint to the left of the window shows the fuselage skin has been repeatedly bent there - firstly outwards at the initial failure and then again as the tail hit the ground and the inertia of the window pane bent it back the other way.
Edit to add: yes, I'd agree it probably wasn't ISIS. More likely one of the various bands of rebels (or their sympathisers) currently getting malletted by the Russians in Syria. If it were ISIS they'd have been trying this against western aircraft in the region ages ago. ISIS, for all their medieval barbarism, are trying to create a state, not another Al-Qaeda style terrorist group.