Physical shutoff via relays is required by the standard. We've just been through a scandal where a manufacturer skimped out on putting them in and had to recall the devices.
Yes, because the frequency of the grid is also a trigger for shutting off the inverter. Inverters generate a frequency which indicates a "non healthy grid" that trigger the shutoff of connected inverters.
At this stage it's all hot air. Nobody has even started talking about how to finance it and the defense minister isn't even 100% sure he will get his requested additional funds for the next cycle. When somebody asked him about the topic he replied that he isn't categorically against it but he would have to finance (and restructure, as the necessary infrastructure for it has been degraded/scrapped) more important topics first.