Yes, although the steps for doing so depend on which exercise system you're using.
The Business Architect Essentials course provides an on-line, hosted environment and a downloadable VM for completing the course exercises. The process for resetting the system differs for each environment.
If you're using the hosted environment:
Navigate to the course overview page.
In the upper left corner of the page, click Options to display a menu of options.
From the menu of options, select Reset Exercise System.
If the reset option is not available, contact self-study support for additional assistance.
If you're using a VM:
You can just reimport the OVA file into VMWare player to create a new VM for your use.
In either case, each exercise has a dedicated application associated with it that incorporates all of the work performed in previous exercises, so you do not need to repeat the preceding exercises to "catch up". You can resume at the Configuring Reference Data exercise.