This varies from teacher to teacher. But it there is no rule that states that you cannot use the same music. I would say it is recommended that you use the same dancer from your core... you already have a rapport with them and they know your style of movement.
As for movements - you can use some that are the same, although the major study is about choreographing for 2-3 dancers and this must be the focus. You really need to look at positioning them, using cannons, group work etc as a way to help convey your intent.
Hope this helps!!