jangus
Hi
JomSocial 4.3 no longer compatible with new Joomla and also use older codes and not supported.
Also the database has been update in the JomSocial 4.5 with messages replace with chat. As these version not available in downloads as well its hard to give a compare chart. You can check the changelog here to see new version changes : https://www.jomsocial.com/features/changelog