Please help me to choose the correct option. I think the both options are correct because I have seen in many contexts where they are interchanged.
Can I mix up the present perfect and present continuouse tense as in the above sentence?. Or it should be "were" or "have been". Please help me.
Your sentence contains the present perfect and the simple present, and the sentence is fine. He 'has seen' in the indeterminate past, and the 'contexts' remain interchanged now.