Automic provides several APIs to access the AE. Unfortunately the version compatibility is not consistent. For this reason, we have started to create an overview of which versions work with which AE versions or not. Perhaps you can provide more information so that we can get a comprehensive overview.Update 2019-07-30: I received the information from @Andreas Buesching that all versions 12.x of the AE.ApplicationInterface can connect down to version 9 of the Automation Engine. Of course, this does not mean that all requests will work, but they are basically compatible.
AE Application Interface 12.3 - Upgrading a project from 11.2 done in C#