Yes, Nokia 8.1 does have the HDR10 support and you can watch 4K videos on Nokia 8.1. You can record 4K videos also.
There is no official communication from the company if Nokia 8.1 will be able to work on the 5G network or not.
Yes, Nokia 8.1 does support the FM radio.
Yes, Nokia 8.1 does have the fingerprint scanner, which is located at the rear of the phone.