The release notes list changes to the API.

To determine the version, use Control Panel, Add Remove programs which will list the currently installed programs.

Also, you can determine from the logs in C:\Program Files\Cisco Systems\CTIOS Client which will show the installation logs and there will be one for each version that got installed. For example, the latest CTIOS Toolkit I installed on my system is 7.2(5) and so there is a file CTIOS7.2(5).log