Is Oklahoma City on an Indian Reservation ?

Answer 1

Probably not, but according to a Supreme court ruling in 2020 a lot of eastern Oklahoma was still reservation land. This article specifically mentions part of Tulsa: https://www.washingtonpost.com/national/supreme-co...

Answer 2

No, a large chunk of the state is considered tribal lands but not to the extant that other reservations are which is why you have cities like Tulsa in Oklahoma built on an Indian Reservation.  Where Oklahoma City is, however, has never been legally considered or claimed by Native Americans and was instead referred to as unassigned lands which is probably why it’s the main city in Oklahoma.