1. Information will not have radar and if given a poor position report and a vague routing, may not realise that your track will take you through a Danger Area. A free utility is SkyDemon Light (others probably also available) which will give you preplanning for active DA's, however the responsibility is firmly with you to make sure that the area is not active before transiting. If it doubt, remain clear- being unable to decode a perhaps complex NOTAM is no excuse
Why not simply ask the FISO/Controller if Dxxx is active?
2. As already said.
You must ensure that you obtain a joining clearance before entry.