personally, I don't really believe in a dream guide, which is probably why I have never seen anyone in a LD claiming to be him/her. I think all DC's are just projections of your subconscious, and it could be a possibility that your dreamguide is a subconscious representation/projection of a special figure in your waking life. If DC are really projections of your subconscious and if your DG is a DC, then obviously it is possible for this "DG" to know everything about you and all about your personality and beliefs, which are ingrained into your subconscious which is what the characters are made of.