Because LiveJasmin is a server-side application, you cannot technically "downgrade" the website itself. However, there are several ways to achieve a similar experience:
When exploring previous versions of LiveJasmine, keep in mind: livejasmine previous version
Would you like a general guide on how to research the history of a website instead? Because LiveJasmin is a server-side application, you cannot
Additionally, are you looking for specific features or functionality that were available in a previous version? Because LiveJasmin is a server-side application