Okay, thanks for the corrections! But going back to the original English question that LizeEmm used:

Mom asked the son if he knew what time the shop opened.
This question could be answered:

"8 a.m. Monday to Saturday, but 11 a.m. on Sundays" [the most likely answer!]
"Today they didn't open until 9:30 a.m., because of a power outage from last night's thunderstorm"

But this answer is IMPOSSIBLE:

"The store's hours are from 8 a.m. to 9 p.m. Monday to Saturday, but 11 a.m. to 4 p.m. on Sundays"

If one expects an answer of this type, the "reported-speech" sentence would likely be phrased:

Mom asked the son if he knew [what time / when] the shop was open.
This implies that the mother's wanted to know: "Son, what are the shop's normal business hours?", and not "Son, at what time does the shop open each morning?"