Its not wrong, its normal to be depressed as you miss him. With depression comes illness... Usually. So pick yourself up, take care of yourself until the next love in your life comes around.
Nope, nothing that you feel is ever wrong.
Keep yourself open to a new crush. You just never know when a new one will come along!
No, why would it be wrong? Just try not to wallow in it too much for too much longer. Two and a half years is enough time to spend being sad over a boy, especially one that's moved away and that you can't change the situation about.
let it go if he is moving away then you also move away and ahead in your life dont think much about it there is much to do....and yes dont be depressed always be happy.just try to shift yourself in other thing you will feel better.all the best.