Before is merely an outline of time in question prior to an event, action, date or time. Beforehand is the description of the duration of time outlined in question.

How do you use beforehand?

ahead of time; in anticipation.
They proposed to make arrangement beforehand.I had made preparations beforehand.It is reasonable to assume that he knew beforehand that this would happen.The police need to be briefed beforehand on how to deal with this sort of situation.

Is it beforehand or before hand?

be•fore•hand (bi fôr′hand′, -fōr′-), adv., adj. in anticipation; in advance; ahead of time:We should have made reservations beforehand.

in anticipation; in advance; ahead of time: We should have made reservations beforehand.