Dear colleague armchair detectives!
Can I summarize what we know so far and make brief description of events?
1) Plane was in relatively good condition and maintained adequately at least.
2) Crew is experienced and rested
3) No suspicious passengers onboard, no major delay or any other inconvenience through ground ops reported
4) T/O without issues and begin climbing OK
5) When reached about intended FL but before leveling something very brief (fraction of seconds) and violent happened INSIDE, plane was broken in parts and falls down.
5.1) This event was so short that crew have no time to complete any action, so it's not stall or similar.
5.2) This even was followed (and possible is cause) of tail section detachment
5.3) Part of this event or it's direct result was intense fire (close to explosion) which destroyed wings section and killed last rows paxes
Now some speculations.
1) Place of event is somewhere middle to tail part of plane, between front cargo door and RPB.
2) I think also that it was below or at the level of cabin floor
...