You will need to downgrade via the Drone Hacks app using a Windows 10/11 PC. In regards to the Care Refresh, If the drone is damaged etc, I don't think Dji is going to worry about your FW version. I have my Mavic 3 on demo FW when it took off...
Yes, to use the 4G Dongle 2 on the Mavic 4 Pro outside of China then you will need the RC 2 and the Mavic 4 must be on the original FW which is 0.0000. Any FW after this disables the 4G Enhanced Transmission.
@GadgetGuy Dongle 2 is not...
I'm in Brazil and could not renew after the free trial period of one year. My question still stands: If I buy a new dongle will the free one year license work again? I suppose that the free trial is already registered on DJI servers and works...