Flyable or not?
Sadly, I'm not a pilot.
After reading through this entire thread it strikes me that the primary question is whether at any point after leaving the ground this aircraft was actually sufficiently controllable to recover it? That question can't be answered until the investigation reports.
I can see that rolling to 90% of bank will get the nose down, and why, but a 747 can't fly at 90% of bank. I can imagine a misconfiguration or control problem resulting in an aeroplane which can remain in the air in a tight turn with steep bank but pitches up to stall again when the wings are levelled. How would you get such an aeroplane back onto the ground?