1.) Yes. When you do a 'backup', it's like a snapshot of everything and every setting on your phone at that moment. When you revert, your phone will have EVERYTHING it had at that moment in time.

2.) Basically, yes. Your contacts, apps, settings, etc. are gone. However, google does a great job of restoring your contacts, and a pretty fair job of restoring your apps, and even a setting or two.

3.) The method I use takes _maybe_ an hour. I prefer to use MyBackup to backup these 'data' things: call logs, bookmarks, sms, and mms. I use it to backup all my apps (.apk only). Then after the perfunctory data/cache wipe and new ROM (and all it's parts if needed) install I let the phone boot up to the "Touch the Android" screen. I will proceed from there and once I get my phone signed back into google and have it starting to sync I set it down and do not touch it for a long long long time. I will NOT touch it and continue UNTIL I see a "xxx applications restored (or partially restored)" message in the notification bar. Then sometimes when I select that message, the market will open with options to restore the rest, otherwise I continue thusly. Using MyBackup, I will restore data and 'select all' (as all I backed up was call logs, bookmarks, sms, and mms). Then when prompted, I reboot the phone. From here, sometimes upon reboot any apps not previously restored _might_ restore, but I will usually just go about either restoring them and/or re-downloading them from the market. And then I will also fine tune: setting custom ringers/notifications, assigning ringers to my contacts, etc.

Hope this was of help to you.

good luck

 

If you have access to a good, fast, and stable WiFi connection when doing this, it might be advantageous to use the four corner trick to bypass activation, then enable your WiFi connection. After that, run market, whereupon it will re-initiate the activation process and start synchronizing your settings and then apps.

HTH