You can test a Sakai Plus install using one of our nightly servers as long as it is running at least Sakai 23.
https://trunk-mysql.nightly.sakaiproject.org
Of course nightly servers are reset every 24 hours so anything that you set up will vanish - and if you mess anything up - your mistakes will conveniently disappear.
If you want access to a server for testing that will not be reset each evening, send an email to plus at sakailms.org.