modal perfects

Question 1

Ability to do something in the past, that wasn’t done

Answer 1

Could have

Question 2

Certainly that something didn’t happen

Answer 2

can’t/couldn’t have

Question 3

certainly or logical conclusion about something in the past

Answer 3

must have

Question 4

A guess about a past action

Answer 4

may/might have

Question 5

criticism or regret conclusion after an event

Answer 5

should/shouldn’t/ought to have

Question 6

Willingnes or disire to do something, which wasn’t actually done.

Answer 6

Would have