Recently, a leaked testing preview build has been uploaded and spread out through archives.

Someone is constantly reuploading it, meaning there's not really a point of trying to take it down.

As of right now, they go by the tag of "fnaf_engine_reborn" edit: Now renamed to grimm foxy

Do not download due to possible virus in the app. The build is called 0.2.1 made in April of last year.
If you want to try it out, do so in a virtual machine (VM)

If you open it and things aren't working. that's because it's a preview and testing build.

TLDR: Do not download any apps that claim to be FNAF Engine Reborn. Specially ones called 0.2.1. It's not official!