If you put a video file into a folder and press play on the folder then while playing you can use options to set the video to replay the video continuously. I’m sure this would work for audio files as well.
I use the box a lot and although it gets warm, I haven’t noticed anything major with heat issues.
I’ve had it on for extended times (up to 20+ hours) and it’s still pretty darn good.
I’ve never used playlists so hopefully someone else here can help with that.
any USB drive should work fine (but take caution with USB 3.0)
hope this helps! 
