In fuel injection engines, what is 'Overrun Fuel Cut-off' (Schubabschaltung) and how should instructors teach its application?

1. The engine continues injecting its normal idle quantity while the clutch is disengaged
2. The driver must shift into neutral and rev the engine continuously
3. The engine control unit completely cuts fuel delivery to zero when the vehicle is decelerating in gear with the accelerator fully released, providing free engine braking and zero fuel consumption
4. The fuel supply is cut whenever the service brake is pressed, including while idling