I have VSR turned on - VSR causes things to run in higher resolutions than the monitor supports. The benefits of doing this is that you will end up with a much nicer image than if you didn't use the VSR.
I am trying to run SR2 in 4K but when I choose 4K and save the resolution and leave the settings it immediately reverts back to 1080P.
VVV This is after clicking save and then leaving the settings and immediately returning. VVV
strange, i had SR2 running with VSR