1) dunno, never used a structure
2) z is depth in clipspace. You can use the z value to render a depth map for example.
3) Normal is interpolated if you use soft edges (smooth) and the triangle's normal if use hard edges (flat mode). Hopefully the mdl format will support that soon.
4) Don't think so but I don't know it.
5) I think it's possible with pro. You need to render a depth map from the lightsource and then use render to texture to use it on your screen.
6) again you need pro

5/6 buy Sphere