There is a note in rig description about simplified version of IK/FK switching present in this rig, so it should't be a surprise - there is NO full fully functional auto-snap IK/FK switch present. sorry.

If I understood correctly you're saying that there is basic IK/FK switch without position snapping. I see in Outliner that there are hidden controls for FK, but how to turn them on and off ?

There is no rig docummentation in the .rar file or on the website so it's hard to get any directions.

Yes, DummyMan do has basic IK/FK simulation - search for "attach to" attribute on hands and legs conlrols.

So I switch the hands and feet to "Attach to" body and hips, respectively, and that gives me FK controls for the shoulders/legs and wrists/ankles, but no controls for the elbows and knees?