When I download a video on the YouTube app, it gets placed at the top of the "Downloads" playlist. So when I play it, the queued video is at the top instead of the bottom. I want the opposite behavior so when I play an older downloaded video, the newer ones play next.
This is something that is not natively supported by YouTube. And since YouTube is a proprietary app there's nothing really you can do about it except requesting for that feature.
I would, however suggest you to use New Pipe. Ir's ad free and open sourced. You can download it via its github page