Perhaps, Mr.Matthews, if you remembered that others view replies to questions, you might have given a fuller understanding of the 'why' it's 'pass' not 'passed', in your first response. There are others who view responses to questions, including non-native speakers with varying levels of English. Your bald statement as to the correct tense lacked consideration for them.
It seems my efforts, at least, do goad you to expand, even though your motive is more a rather ugly competitive spirit.
My first response gave the required answer to the core question, i.e. that the plain verb-form "pass" is required as a result of the presence of the dummy auxiliary verb "did". The reason for its presence in the OP's particular example is a little complex (it has nothing to do with questions) and one that I could have explained but chose not to for fear of confusing the OP.
Nevertheless, had you managed to explain why subject-auxiliary inversion occurs in declarative clauses, I would have passed quietly over your answer without comment. But your answer was defective in that it focused entirely on inversion in interrogatives (questions), which is irrelevant here since the OP's sentence is a declarative one, not an interrogative one.
You made no mention of certain elements triggering inversion when fronted; more specifically, you gave no explanation at all as to why the word "only" can trigger inversion when it is fronted, yet its presence in the OP's example is precisely the reason that it exhibits inversion!
If you intend to explain subject-auxiliary inversion, at least do so adequately, with a fully supportive explanation of why it occurs in declarative clauses like the one cited by the OP.
However, we can only assume that your omission of crucial points in your answer is due to the fact that you are clueless about this aspect of English grammar.