slip and turn,
Can't answer all yours, but in brief.
A "deep stall" had nothing to do with the engines, but it happened on T-tailed aircraft, when an excessive pitch-up led to the stalled turbulent flow from the wings totally "blanketing" the elevators, so that the aircraft refused to pitch down even with full down elevator, and just went in nose-up with little forward speed but a very high descent rate, and totally uncontrollable.
The 'hint' about the engines is not totally irrelevant, because most of the T-tails involved in such accidents had rear-mounted engines.
CJ