I don't know if anyone has actually beat it yet but its HARD, maybe a bit too hard. I've gotten to about 2 and died to Mario. Also the rest is spoilers about the ending.

So, it takes place after the good ending of FNaW 3 where you get shot. This whole game takes place in a nightmare(like the name says lol). This isn't the end, there will be a sequel, it won't be like "Bruno's Nightmare 2" because Bruno is dead, he won't be having nightmares anymore.