You can search for Iguana Gaming on Youtube. She just did an interview with the maker of the Mobile version of Ark about the dungeons. I can answer some of your questions based on watching that video.
1. God mode is not allowed in the dungeons. Certain rooms or areas could be completed without triggering the required pre-request for advancing to the next area, thus creating bugs in the game.
2. Creature difficulty will be scaled to server difficulty. Traps will be same difficulty for everyone. Single player boss can have 50k health.
3. There will be dungeon exclusive creatures, I do not think that all the rest of the new creatures will just be dungeon exclusive, but do not know that.
4. Question not answered, but there will be different environmental elements in the game.