Have you ever (fail) important exams/tests?
failed
Have you ever (see) a ghost?
see (Do you believe in ghosts?)
Have you ever (lose) something important?
lost
Have you ever (touch) an elephant?
touched
Have you ever (eat) unusual food? What was it?
eaten
Have you ever (fly) a plane?
flown
What is the best holiday you have (have)?
had
Have you ever (fall) asleep at the lesson?
fallen