1. Only when you've applied the patch mentioned in #3
2. The monitors prefs, or in the Monitors menu item, if you turn it on in the Monitors prefs (system prefs>monitors). It won't show up though, until you run the patch...normally iBooks ONLY do mirroring, so you can't turn it off.
3. Apple doesn't support it, and Apple probably doesn't like us posting links to it, but it DOES work, and I know many people who have used it.
4. It's a limitation of the iBook (before the patch). Again, see #s 1, 2 and 3 🙂