Here's what I was able to find:
Players Handbook (2E, 2nd printing) page 137
Undead bound by the orders of another simply retreat and allow the character and those with him to pass or complete their actions.
Free-willed undead attempt to flee the area of the turning character, until out of his sight. If unable to escape, they circle at a distance, no closer than 10 feet to the character, provided he continues to maintain his turning. No further die rolls are needed.
If the character forces the free-willed undead to come closer than 10 feet, by pressing them into a corner, for example, the turning is broken and the undead attack normally.
Dungeon Masters Guide (1E) page 76
Good clerics cause the creature to move directly away from his or her person, and stay as far away as possible for not less than 3 nor more than 12 rounds, moving at full speed for the duration if at all possible. The turned undead will be able to come back again, but they are subject to further turning by the cleric.
OSRIC page 123
Turning lasts for 3d4 rounds. While turned, the creature must move away from the cleric at its fastest possible movement
rate. It will attack a creature that is directly blocking its escape route, but otherwise may not fi ght.
The cleric or paladin must be holding his or her holy symbol to make a turning attempt. In most cases this will preclude
attacking on the same round, and the cleric must sheathe or drop his or her weapon (or else set down his or her shield).
***
Like most situation, the ruling would ultimately fall upon the DM, but here is how I would respond to your questions:
ToniXX wrote:1. What exactly do turned undead do? If they can exit the room would they? What if there's a closed door? Some undead can open doors, it would seem. Do they flee as far as possible, or to just a certain distance?
Again quoting the 2E Players Handbook:
"
Undead bound by the orders of another simply retreat and allow the character and those with him to pass or complete their actions.
Free-willed undead attempt to flee the area of the turning character, until out of his sight. If unable to escape, they circle at a distance, no closer than 10 feet to the character, provided he continues to maintain his turning. No further die rolls are needed."
"
Flee the area of the turning character" and "
If unable to escape," to me, sounds like they would attempt to leave the room if possible. If not, they will move as far away as possible with that distance being at least 10 feet.
ToniXX wrote:2. Does the turning cleric need to continually focus on the turning, or once the turn is done, can he/she return to combat with other creatures?
From the sound of "
provided he continues to maintain his turning," it sounds like the cleric must continue to turn and not take other actions. I'm not really sure about that, though?
ToniXX wrote:3. If a turned undead is attacked, it will obviously attack back, the turn being broken. But, if other undead are turned with it, would the turn be broken on them as well?
I didn't see where this was defined in any set of rules, but I would probably rule that turned undead that haven't been attacked will remain turned. I wouldn't view it much differently than a cleric turning a skeleton and a zombie, but not a vampire. Just because the vampire isn't turned, the other lesser creatures still can be. Using that same logic, just because one of the previously turned creatures has its turn broken, that probably wouldn't affect the turning capacity of the other turned creature; it would, at least in my ruling, still remain turned.
There were 310 pages on Dragonsfoot when performing a search on the keywords 'turn undead,' but I did find a few discussions which had some pretty interesting stuff in it:
Questions about Turning (High level slanted)
Turning Questions
There were a few others which I didn't get a chance to scan through, but my laptop battery is about to die on me so I'll need to submit this as is. Hope it helped... or at least got the discussion started.
- Dave