Snapchat allows you to record video and play it in rewind or reverse mode (similar to boomerang in Instagram) when you share your video on your Snapchat Story with friends.
1. Make sure you have the latest version of Snapchat installed.
2. Record a video.
3. Now, you must apply the reverse filter. Swipe left on the screen about 6-8 times until you see the <<< icon shown below and apply it.