Acquia Cloud makes a daily backup of each database and keeps it for three days. OIT can make can make additional backups of any database; send a request to firstname.lastname@example.org to download any backup and send it to you. Backups generated by OIT will be retained for 90 days.
The code is in a repository on github.umn.edu. You also can keep local copies of it.
Your uploaded files are kept separate from your Drupal codebase and database, using a symbolic link to your website's /files directory. Acquia Cloud makes internal disaster recovery snapshots of your files, but these are not available for customers for normal backup purposes. The disaster recovery backups are only used in the event that the Acquia server itself is rendered unusable and are not available for ad-hoc backups. Currently, generic backup of files is the responsibility of the site owner, but OIT will be looking into providing a generic backup solution in the near future.