No. You could say 'what have you prepared for breakfast' or 'what did you prepare for breakfast' instead.
"Your sister usually has breakfast at half past eight."
It depends on the context. Both of these examples are correct: Ask permission of her. You need to ask for permission. The former is slightly formal, while the latter is more casual.
The correct sentence is the following: "What were you doing from before?"
Yes, it is correct to ask "Are they an item?" when inquiring about the relationship status of two people to find out if they are romantically involved with each other.
No, "hows you" is not grammatically correct. "How are you?" is correct.
"What do you like for breakfast?" would be correct.
"Waiting for our breakfast to be served" is correct.
Breakfast and lunch were . . . "
The correct spelling of the plural noun is "dinners," and "breakfast" is correct.
Yes. It's not a complete sentence. You must say what was prepared. But that is correct phrasing. Paperwork was prepared for this transaction. I was prepared for his resignation. Dinner was prepared by the children. Was the package prepared for shipping? The report was not prepared on time.
"Have had" is correct. For example: The children have had their breakfast.
Yes, this is the correct way of telling someone to "cook breakfast."
It depends who you ask. Soup can be for breakfast, lunch or dinner.
"Did you have your breakfast" is the better one to use.
For breakfast I like milk and pancakes.
It is NOT correct; it should be: He has neither had his breakfast nor IS HE coming out of his room (the inversion is used here for emphasis and effect).
The correct spelling is breakfast (morning meal).