A bit more info on Q2, If you think of the ASI as a dynamic pressure gauge rather than a speed indicator that might help, the needle points at a speed because thats useful to us pilots however its actually measuring dynamic pressure i.e the amount of air molecules passing over the wings, the wings are only interested in the density of airflow passing over them not speed, at altitude you have to go much faster in reality to achieve the same volume or density of air passing over the wings therefore the same dynamic pressure as the ASI reads dynamic pressure the aircraft will always stall at the same indicated speed or pressure to be more correct.