Мама спросила сына, знает ли он, когда открыт магазин.
The present tense.
Доктор спросил, болит ли голова.
Я спросил Мишу, было ли трудно... (because asked / had been)
So, is there no accounting for the fact that the action actually happened in the past? Is it absolutely unacceptable to use the past tense or is the rule flexible?