Under what condition is a Category B learner driver permitted to drive on Swiss motorways (Autobahnen) or expressways (Autostrassen)?

1. From the very first day of receiving the learner permit (Lernfahrausweis)
2. Only if driving an electric vehicle during off-peak night hours
3. Motorways are strictly prohibited to all learner drivers until after passing the practical test
4. Only when the learner driver is judged ready for the practical test (prüfungsreif) and is accompanied by an authorized supervisor