"Are you a boy?"
Translation:Czy jesteś chłopcem?
yes, you can skip "czy" in questions, and you can always skip "ty".
Keep in mind that using "czy" makes a question more clear, especially if you are not a native speaker and have trouble with pronounciation.
Maybe someone asked before, but what is the difference between "chłopcem" and "chłopakiem"? Thanks in advance :)
They are both Instrumental forms, so let's rather discuss the Nominative, basic forms.
The difference between "chłopiec" and "chłopak" is a matter of age. "chłopiec" is a younger boy, "chłopak" is older. But there's no set border, it's a subjective thing. Personally I'd say that "chłopiec" should 'end' not later than 12-13. Rather earlier.
Also, "chłopak" means "boyfriend", if it's "someone's chłopak".