Mapping questions

[EntityReborn]

1. Is there a way to do crazy gravity stuff, as per the TNM mod, in the Voodoo shop, without completely rewriting the game? If so, how would I do this?

2. Is there a way to, for instance, have a door sitting in the middle of an empty room, and when you open this door, you can see into a new area? A la Portal, but mapped in, without the gun, and just a regular door.

3. Can you take what a camera sees and post it onto a texture?
3b. Is scripted texturing possible?

What other insane mapping hacks/tricks are there out there?

EDIT:
As per 1, I found http://udn.epicgames.com/Two/ExampleMapsWarpZones.html but trying to follow this doesn't work. Example file attached.