Yes, you can use 2 4G Sim cards in this phone.
Yes, Nokia 8 does have the Gyroscope sensor.
Yes, Nokia 8 is a true 4G network and it shall work with Airtel VoLTE.
Yes, Nokia 8 does have an OTG support as well.
It’s safe to say that if a smartphone like this had shipped from the Nokia stable a few years ago, the Finnish company might never have had to step back from the mobile business.