Is he gay/bi, and does he like me?

Well I think it's quite obvious that you two are really close, the only thing is building up the courage to ask him, make sure you do it at a good time and with no one else around if possible. Thing is, if you're planning to ask him if he's Gay/Bi you should probably be planning to confess your feelings, it flows well in the conversation. It can be a very hard thing to approach directly, if you can try and find yourself in a situation in which you can causality ask it without it sounding too sudden. But ask yourself now, do you have real feelings for him? Not just a little interest, but love? You're only 13, which is pretty young for a relationship, you're entering a delicate stage where you're questioning your sexuality a lot. Be very sure you know what you're doing before you do anything, if you are sure though, go for it! Just make sure to let him know you'd still want to be friends should he say no.