Yes, with Nokia 8.1 you can record 4K videos @ 30 fps.
Nokia 8.1 comes with the Android Pie out of the box. You will also get Android updates for the next 2 years.
Yes, Nokia 8.1 does have OIS support.
Yes, Nokia 8.1 does support Qualcomm Quick Charge. It also comes with 18W fast charger.