A
Depends on the phone. Hardware limits the card size, not just software.
AFAIK you also have to take into account the highest transfer speed the hardware is capable of, as well as how much power it can give. Just because something can handle SDXC 64GB, doesn't mean it can handle SDXC 2TB.I don't think that's really true. It should just depend on exFAT support in software.
That said, some manufacturers include the exFAT software support and some don't. This can potentially be worked around by installing a custom rom.