It does. I’ve been using it, I tested it, it works. They just get the info that I am “currently unavailable” and I get SMS with info on who tried to call me when I was “unavailable”. Just like airplane mode, but I get to keep data and SMS.

2G will be used only for emergency calls.

4G/5G doesn’t support traditional voice calls like 2G/3G did. Only VoLTE, VoWiFi and VoNR which are a total mess with lack of one universal standard.

But they can try, if that’s what you meant.