They are all correct, and natural, with regard to grammar and sentence structure.
I assume you noticed that (1) and (3) both mean the same thing, while (2) means something quite different. (2) actually is a somewhat unlikely thing to say. It is hard to invent a situation in which it would make sense. This is the best I can do:
Almost everyone was in the classroom on time, but one boy arrived late. He was still in the hall outside the door when the bell rang.
"You're late again," said the teacher, irritably. "I'm going to make you stay five minutes after class when the bell for lunch rings."
So the students in the classroom ate lunch first. The boy in the hall ate lunch later.
although your sentences are good they are a little bit short and do not provide much detail.
Or allow you to practice proposition or pronoun combinations
"The boy in the hall ate HIS lunch later"
"The boy ate HIS lunch later in the hall"
"The boy ate the lunch later in the hall"