have you ever with past tense
 

Could I use know? (not knew or have known)

(A teacher asking a student in class)
-Have you ever watched a film of which you already __ the ending.

My opinion is, 'have you watched' indicates you are talking about the past up to now, not into the future. So knew and have known are both correct, with almost no difference in meaning, and know is wrong. But my friend says the sentence could be used to talk about a general situation, where there's no past or present or future, and that know is also correct. Which one of us is correct?

Re: have you ever with past tense
 

Both could be used - knew or know, for the reasons you say, though knew sounds more likely to me. But the use of "of which" is strange - much too formal for this sort of conversation :
Have you ever watched a film where you already knew the ending?

Re: have you ever with past tense
 

Excellent answer. Thank you.