I have no idea either, but it should actually work. The question is rather whether the corresponding suppliers offer roaming in this country or if you bring the device with you, the frequencies of the suppliers are supported by the device - I think the latter was only a problem in the past

I have used the router with 2 SIM cards from CH providers. US and Asia not tested, but see no reason why a SIM look should be installed (SIM look is actually new for subsidised mobiles). SIM format must be Nano (there are hardly any others). According to the manufacturer's information, there are also no restrictions. So in my opinion 99% sure that it works with all SIM cards, but not tested.

No idea