1 is a sentence, 2 is a sentence fragment, 3 is a sentence, 4 and 5 are sentence fragments.
Explanation:
A sentence fragment doesn't fully make sense, because it doesn't give enough details to form the sentence fully. "He walked away" would be a sentence because it has a subject, "he," and a verb/predicate, "walked away," but "walked away" would be a fragment because it only has a verb (or predicate) and not a subject.
