- Yes. You can choose the same drive for all your shares if you like, and if there's room on the drive to back them up.
- Windows Home Server uses hard links to previous versions of unchanged files. This allows you to back up a share repeatedly even if all the backups wouldn't fit otherwise. However, if a share won't fit on the backup drive you won't be able to back it up; drive spanning isn't supported.
- Folders and files. There's one top level folder for each backup you've done to a drive, then your shares will be under those folders.
- Yes.
There's no technical brief specifically for this feature. It's a relatively small and simple concept; you're just copying files from the shares to the backup drive.
I'm not on the WHS team, I just post a lot. :)