1) having a crush on someone but knowing for sure they don't love u
Hmm..slowly but surely let him go, one sided love isn't fun at all.
2) having a good friend that u don't love say they love u
I'd tell him the truth that his friendship means more to me, and that's how I've always seen him.
3) having a crush on someone who you're too afraid to confess to
Sometimes it's okay for a while, daydream and things, but it's also hard to know what he's thinking and if he thinks about you like you think of him. Usually in this situation, I'd have my friends find out for me or if i have enough courage, i'd tell him.
BONUS QUESTION!
how would you try to get the person you have a crush on to like you back
be yourself, if he can't like you for who you are, then he's just not worth it.