Based on other conversations, this literally says "the plate of the breakfast," but what it means in English is "the breakfast plate/dish." To say the plate of breakfast would require rephrasing, it seems, to something such as το πιάτο με τον πρωινό, "the plate with the breakfast." I think το πιάτο πρωινό would work for "the plate of breakfast," but that needs confirmation from a Greek speaker.
Correct usage is "the breakfast plate/dish". I have found one use "the plate of the salad" and deleted it because it's wrong. It's "the salad plate".
It's not really said that way. You can say "the breakfast plate" instead.
Does πιάτο mean 'dish' both in the sense of the plate the food sits on, and the food itself ("a tasty dish", "a spicy dish")? Or is πιάτο just the plate you put it on?