1. Each AI saves *all* it's data in it's .knw files. That includes all knowledge about all cars and all knowledge about passing, etc.
2. The AI saves it's data when crossing the finish line.
(On longer tracks you can notice that when the field crosses the finish line. The framerate gets jumpy because the knw files are written.)
3. The AI always learns. In practice, singleplayer, multiplayer, quali, race, always.
Vain