I think you might have to use different particles to say "make breakfast delicious". Instead of saying "a delicious-being breakfast make" which is what this translation is saying, maybe you would say something like "make the breakfast to be delicious" so you would say something like 아침을 맛있게 만드세요. They're both very similar sentences though, so maybe your translation should be accepted :)
They're different sentences. Imagine using them. 'Make a delicious breakfast' is telling someone to make breakfast, and also specifying that the breakfast should be delicious. 'Make breakfast delicious' is an instruction to alter or change breakfast so that it is delicious e.g. 'make breakfast delicious by adding maple syrup' or 'buy our cereal and make breakfast delicious.
Try it out, imagine your friend was sitting there and you wanted them to make you breakfast. So you say to them "make breakfast delicious." They would be confused.
I don't know. This is a command that sounds polite in Korean but potentially unpolite in English bc it does not have "please" in it. In my understanding, adding 시 (which becomes 세 in this sentence) makes a polite command like adding "please" in English. I came to ask about this because I think this should be translated with "please" in it to avoid misunderstanding that this is pretty polite in Korean, not rude