The graphics are impressive. Is this standard with the Unreal Engine or do you need special settings (I am a hobby developer, but have never done anything with the Unreal Engine)?

I pressed the O key a few times and don't see any difference. How about displaying the status?

I have a higher resolution than full HD. Is the game rendered in my resolution or in FHD?

About graphic setting nothing special, just some filters like Chromatic aberration o vignete are applied. After that using the UDS (Ultra Dynamic Sky) plugin does all the work due you can set morning, sunset, night,etc... just moving one slider called "time of day". After that more than settings, having good materials is essential too.

You need to press 0(zero, the number) not O.

About last question , the game should be rendered at your monitor resulution, 1080p, 4k or whatever, but cant confirm 100% due i not tested.