The majority of the API endpoints have information in the Open API specification (i.e. Swagger docs) about what version of ACS that is required (i.e. in the API Explorer).
This version information is usually available in the beginning of the API endpoint description, as in the following screenshot:
Note that an API endpoint can be supported from a specific patch version of ACS, such as in the following screenshot:
If you are running an earlier version of ACS, which doesn’t support the API endpoint, then you would need to upgrade your ACS installation before starting to use this endpoint.