As far as I know, you are correct on all three points. Depending upon which PLC you are using, you will have to make your own symbols. I've had to make symbols for my CPUs, Ehternet Cards, and in some cases, power supplies. These are not parametric build, just plain ACE symbols with wire connections if needed. The names start with PLCIO so that the catalog lookup dialog appears the same as the parametric build symbols.
Since I have my own custon symbol library, I don't keep up with what comes with the JIC or IEC set. It would be quite a task for Autodesk to include symbols for every electrical/electronic device available world-wide. Plus with new devices appearing almost everyday it would be an even bigger task to keep up with that. So we have to make our own from time to time.