Manna asked Rohan, "Have you sat in a trolley bus before ?"

In direct speech, the question is: "Have you sat in a trolley bus before?"
To convert it into indirect speech, we use the reporting verb "asked" followed by the reporting clause "if" or "whether" and the appropriate tense. In this case, the tense remains the same as the original question, so "have" becomes "has" in the indirect speech because it's referring to the present perfect tense.
Therefore, the correct conversion is: "Manna asked Rohan if he has ever sat in a trolley bus."