Hi @danbjoseph!
This isn't possible at the moment using the frontend alone. For example, forms can be deleted in the frontend, but project's can't. (There's been some discussion around project deletion here.)
That said, project deletion is possible using the API. So one option for you might be to delete projects using the API, then retire web users using the frontend or API. In most ways, Central would then look like it does after it is first installed. However, there would be some differences. For example, the server audit logs would continue to show past activity.
Would that be enough for the demo? There might also be a Docker command to reset the database, which @issa would know.