During the Development of Sinister Turmoil, many different versions of the game / teaser games were released to the public.
Here you can find a full record of all of the games we could find.
Freddy Demo
This demo allows you to play as Sinister Freddy walking around an asylum, getting used to animatronic controls.
Awaiting Input_
Awaiting Input_ was a teaser game solely developed by the co-dev on Sinister Turmoil, TheSparky556.
Awaiting Input_ is a game about solving ciphers to unlock different codes that you can use to unlock Concept Images, Unused Audio Files, BTS Renders, and new Renders of characters unseen before.
This game doesn't exactly have much to offer, but it is said that the events of the Secret Ending are canon.
On a later date, it will be revealed in a video how to get to the secret ending.