Thanks for your response. Can you please confirm that what's happening when trying to switch from USB input to Line in ("Line in is unavailable when a device is connected to USB".) is legitimate behavior and there's no workaround other than opening the armrest and unplugging the USB device?
Again, it's sort of counter-intuitive because the line in will play happily while a USB device is connected *until* I actually play from the USB.
Following this link takes you to a page where you can follow the "Exploring Entertainment by voice" link to a more detailed list of commands. The list of available commands does appear to be complete for the 2012 Focus with Sync/MyFord (no touch). However, at the top, it says: "SYNC® voice commands can control your AM/FM radio, SiriusXM Satellite Radio, USB media player, or Bluetooth® Audio device.27 "
The "27" is probably some fine print somewhere (which I couldn't find) but the part about controlling the AM/FM/Sirius radio, of course, doesn't work on these models.
It would be nice if Ford could clarify exactly what features are available at what level. My "in-car technology specialist" who "worked with me at delivery" (10 minutes sitting in the car pressing buttons) was unable to explain it clearly, and may even have been wrong about some of the capabilities he described. Of course, at that point, you get what you get, but there should be someplace that clearly spells this out before that point.
Again, thanks for your time and effort in clearing things up.