Nokia 8.1 comes with the Android Pie out of the box. You will also get Android updates for the next 2 years.
Yes, you can use 2 4G SIM cards at the same time in Nokia 8.1.
Yes, Nokia 8.1 does have the 3.5 mm headphone jack. It also has Bluetooth A2DP support.
Yes, Nokia 8.1 does have the hybrid sim slot.