(1) TAS stalling speed goes up, IAS and CAS stalling speed should stay about the same. If you look at the basic equations, W=½.Rho.V².CL.max at the stall, CL.max stays the same as does weight. So, the player is ½.Rho.V² (known in the trade as q, or dynamic pressure), and the aircraft will always stall at the same value of that. So, as density (Rho) goes down, TAS (V) must go up. But an ASI is actually a pressure gauge, measuring q, so it always happens at the same IAS for the same weight,
(2) DR is a combined yawing rolling oscillatory mode. Most aircraft will do it, and you can generate it by rapid aileron or rudder inputs. In a well adjusted aircraft it'll damp out, in badly adjusted one it won't - usually because of poor damping in one or both of the two axes. DR is identifiable by the nose weaving a horizontal figure of 8, or the wingtip describing an oval. The ratio of horizontal to vertical dimensions of that oval are roughly the ratio of directional to lateral stability - normally if not fixable by other means a yaw damper (SAS) will be introducer into the axis with the greatest static stability. Rarely a problem on GA types or airliners, a real embu99eranceance in fighters since any but the best damped Dutch Roll stops you getting a guns lock on the aircraft in front. You can induce DR deliberately by going "left-centre-right-centre-release" on the rudder pedals at a period of about 2 seconds for a light aircraft or 5-6 seconds in an airliner (observing of-course the rule of not-more than 1/3 rudder above Va).
(3) Ask a systems engineer.
Hope that wasn't too simplistic, if you want me to expand just say.
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