No, DH is an app on its own. To download and flash the FW is free and you don't need to pay. Please note that the 4G Transmission will not work if you are using any FCC hack. Download the app from below link.
https://drone-hacks.com/
Yes, You can downgrade via the Drone Hacks app using a windows 10/11 PC. When you try to downgrade, The drone Hacks will not actually recognize the Mavic 4 Pro but don't worry and just go ahead. Ensure you download the correct FW from Dank...
Those dots on 4G means 4G Enhanced will work. Ensure your sim has enough Data. You just need to play around with your sim settings and it should just work.
He would have got it from Dank Downloader. This is the only other place that offers all Dji drone FW.
@emirkurtpro I would not recommend installing that FW. Its beta FW and will void your drone if it crashes
Honestly, I don't think it will be opened up for the Mavic 4 Pro. If they end up allowing the RC Pro 2 to work with 4G for the Air 3S then we will have a chance but unless that happens, we are out of luck. For me, because NZ has been added to FCC...