I wrote "the boys love food", why isn't it correct?
Querer is only really used that sense in a platonic sense toward people or pets and the like.
querer = want things/love people, dogs, horses, etc.
When does "comida" means food? And lunch?
in a general meaning, 'food' is comida. Lunch is just a particular case, isn't it? It translates to 'almuerzo'.