Some answers are; The lodges seem to be intertwined and the area we usually see is some kind of "lobby" between them. Good Coop may possibly exist in the "good" section. I'm not sure that the 25 years is in any way significant other than it's taken the "good" lodge members that long to figure out a way to pull Bob/Evil Coop back in and release Good Coop back to some level of the dream world that we all exist in.

"Untarnished?" He's trapped in another dimension while his evil twin murders and rapes his friends and loved ones. He gets "out," tries and fails to take Laura "home," and ends up as Richard, just another guy confused in Twin Peaks (or one of the Twin Peaks), unsure what year it is.

Black Lodge/White Lodge. White zigzag/black zigzag. Yin/Yang. Red room is a "waiting room." Seems to be a portal/prison for travelers between dimensions, good and bad. Perhaps "evil" is just a linguistic reaction to an unnatural place. And to the murderous entities, of course.