When you record a video at 60 fps, how can you play the video back at 24 fps?
Using VLC player:


play the video
tap the screen to bring up the controls
click the three dots button
click the"playback speed" button
adjust to 45 - 50% 
done


It doesn't get you exactly the 24 fps but it's something!

I would love to have a way to export the video at 24fps. Or better video editing for built-in Android apps.