The Dreaming- When you don't have Dreamwalker

If you do NOT have Dreamwalker, or any such thing that gives you this ability, what are your limitations when you are in the Dream?  Like, does it function like Medium where, unless you have this skill, you cannot interact at all, or only while in the presence of a Dreamwalker?  Or is it more like the Dark Passages or Spirit Realm?

-Can you use Skills on yourself or others while in the Dream?
-Can you use Martial skills?
-Can you cast Magic on yourself or others while in the Dream?

Thank you!