What is the difference in translation/meaning between these two different grammatical constructions:
Er müsste es getan haben.
Er hätte es tun müssen.
Another related question: What happens with this meaning when Konjunktiv in these sentences is replaced with Präteritum/Perfekt?
Er musste es getan haben.
Er hat es tun müssen.
All four examples seem to have identical meaning to me, and I am sure they don’t.
Related to this question.