A: 21 days. After this period, the file's electronic rights management should kick in and the file will no longer be accessible.
A: Up to ten.
A: If you are finished listening to your recording before your loan period has expired, you can log in to your account, click the "My Collections" tab, and click the "Return Now" button under the title with which you are finished. Otherwise, the checkout will simply expire after 21 days and the recording will become inaccessible.
A: MP3: Yes. However, It is no longer possible to play protected rbdigital audiobooks on WMA devices such as Sansa, Zen, and Sony Walkman. Non-protected titles can be transferred. According to rbdigital's help page: "You can still listen to protected titles in the rbdigital Media Manager, stream the titles from your library’s rbdigital website, or listen to the title with one of the rbdigital mobile apps on Apple, Android, or Kindle Fire devices."
Links to these apps and more instructions can be found using the tabs above.