If he's trying to play hard to get then he likes you. Most times when guys ignore girls who like them, they aren't really interested in anything with this girl other than the obvious things that guys want. If the girl is really persistent, keep trying. Although its like trying to run underwater, pretty difficult if the guy is flat out uninterested. If nothing change, then it is what it is. Just know that maybe your not right for each other if he's not showing much interest :/
truly depends on what kind of person he is.
may be he is shy towards you? try smile to him. see what happen next. If no respond, just move on, leave him.
He might like you and be shy or he might actually just not know you exist or just not want to know you - no way to know for sure without more details
that's the question I'm trying to answer for 13 years!