Translation:What time do you eat lunch every day?
I know "what time do you eat lunch every day" is the literal translation but should "what time do you eat lunch?" also be accepted? Or maybe "what time do you usually eat lunch?" "What time do you eat lunch every day?" doesnt really occur in english where the "every day" is implied. Why would "every day" be important here?
All the sentences you named have perfect literal translation in Chinese. Without 每天 in the sentence the meaning can also be implied in Chinese too in relevant context, if available.
I think the question of @peter.olieman was trying to clarify the importance of 每天 in a sentence. I answered while there is a literal translation for every example, it doesn't mean that without literally translating the sentences in such ways the concept of "everyday" or "usually" would always disappear. Chinese rely on the context to a greater extent than English, so whether a word is needed often depends on the context.
BTW I think "What time do you have lunch?" in English can be used for asking the lunchtime of a particular day or the usual lunchtime given the right context. Isn't it?
What time do you eat lunch? --> 你几点吃午饭 The meaning will be different as the scenario will be more like a coworker asking when you want to go to lunch on the day of the lunch.
你每天几点吃午饭？ asks about your habit. Having said that, "What time do you usually eat lunch" would imply the same meaning, but would not be a literal translation.
I think Diego meant is there a correct sentence including 都 if it’s a question eg 你每天都几点吃午饭?
After all, 你每天都5点吃午饭 (...or something like that) is a good sentence. Can/should it be in a question?
These sentences would be fine:
This is also alright but a sarcasm rather than a real question:
What time have you been having lunch everyday (afterall)?
It would have been weird that you hadn't got stomach problem.