Navigate to your local fork of the course repository. You should be able to view the history of the commits:
git log
Choose a version you'd like to "roll-back" to and locate its identifier, or "SHA" (e.g. 28a7b0c7281264dd5e519a9a18a9acdb2bb849d9
). Then revert to that version:
git reset --hard 28a7b0c7281264dd5e519a9a18a9acdb2bb849d9
Verify these changes by re-inspecting the version history:
git log
Nice! Afterwards, you may want to refresh your fork to return it to its most recent state.