does it ''applied'' to every WH questions ??
is there any grammar mistake in the above sentence ??
should it be '' applied'' or ''apply'' ?? and why ?? when shall i use ''applied'' if it's incorrect??
Yes, that was a mistake.
When you use the verb "to do" as an auxiliary verb, the other verb is in the bare infinitive form -- that is, the "to VERB" form without the "to."
Does that apply in this case? Yes, that applies here. (present)
Did that apply in that that case? Yes, that applied there. (past, positive)
Did that apply in that that case? No, that did not apply there. (past, negative)
Did you see that? Yes, I saw that.
Did he pick her up at the airport? Yes, he picked her up.