Can you take other peoples birth control if they give you a month's supply and if so what will happen if you only take it for a month and then stop?

No you cannot take another persons birth control. There is a LOT of different birth control, each prescribed to one specific person for a specific reason and because of this it may effect you adversley. If you were to do this you will mess up your menstrual cycle and your Ovulation cycle which in turn can cause irregular periods. You may also experience a variety of symptoms. If you want birth control then see your doctor about being prescribed some. Also during the month of taking birth control you will not be protected against pregnancy completely.