II - Worlds appear in KH, could you please give an explanation of the means of coming and going between them?
Concerning the structure of worlds, first Sora and the Disney characters, and where ever we dwell, these so called normal worlds are attached to a World of Light. If all of these exisit at the same level and you imagine them all sitting on top of a plane, there is also plane of existance on the other side where the World of Darkness exists.
At present, there are 4 worlds in between these planes that have appeared. A) Castle Oblivion, B)Twilight Town, C) Yen Cid's Tower, and D) The World That Never Was. Constructed in this manner, Light < C < B > A > D > Darkness, you can imagine 2 planes with stairs ranging between the worlds.