When change the framebuffer resolution by calling
Screen.setResolution(1920,1080)
Screen.currentResolution, Screen.width, Screen.height reports back the new resolution 1920x1080.
Screen.resolutions gave me empty array (tested on real android device).
I am unable to get back the original resolution which was a native resolution of the device. Do I have to remember the native resolution or is there a way to get that through unity API ?