Sorry for such a dumb question, but how can I verify that my old G4 DP 1 GHZ came with USB 2 or not? System profiler does not spell this out for me - or maybe I am missing something?
No.
The first PowerMac G4 with USB 2.0 included is a Mirror Drive Door model.
If you look in the System Profiler/USB, you would see a listing for Hi-Speed. No Hi-Speed listed - no USB 2.0