depends if you send them a drawing or a solid model. As a rule, you should not send a solid model without a drawing to ensure your intentions are met. For example, a solid model may not convey tolernaces.

A 4.5mm hole is just that. Unless you tell them to tap it to an M4, you will not get at tapped hole. Also worth noting that if you can accept a drilled hole, make a note that the drill point is acceptable. Flat bottomed holes are marginally more expensive.