Can I restart from the beginning?
Yes. Each course you own has an information page where the rating and course comments are displayed. On this page, for each course, there is an "Owner Options" section on the right, with a "Restart" hyperlink.
Using it will wipe your learning progress for this course so you can start again from the beginning. This is useful if you have overloaded yourself with work on the course and would like to start again at a more manageable pace.
Note: This does not wipe your leaderboard score.
This action cannot be undone, and it has a confirmation window, please proceed with care!