"Are you a boy?"

Translation: Czy jesteś chłopcem?

[Aichatr]

Is it okay to only say "Jesteś chłopcem?"

[immery]

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.

[symphony.ali]

Maybe someone asked before, but what is the difference between "chłopcem" and "chłopakiem"? Thanks in advance :)

[Jellei]

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".

[TheShinigamiRyuk]

What case is boy in?

[Jellei]

Instrumental.

[Aiphos71]

Can you use "to" here?

[Jellei]

No. You can't use the "to" construction if on its left side you have a pronoun ("Czy ty to chłopiec?" sounds quite bad).