If you hadn't started your period your period is most likely to start. and if you have.. it might be your time of the month soon
It is just "old blood" from the last period. Very common. Or if you haven't started yet, it's probably your first period :)
its your period mosty likely. if you havent started it yet, you have. if you have, its normal
Montly Mestransation Cycle.
Depends on where it is coming from; but brown/black/red is usually blood or a sign of bleeding - old blood.