The demo goes a little further than you can normally play and you can discover a little more of the (disturbing) story.
The zip archive contains a cheat engine table with a few teleports to normally unreachable locations.
The teleports should only be used after you have reached the curtain! Don't click on the curtain but use the table!
The code for the toy room is pretty easy to find out. Grab the screwdriver and go downstairs. You will see 4 doors and a woman, talk with her or not, it doesn't matter. Use the teleport again (4th door). Interact with the woman (story info) and then look for a ventilation shaft. Use the screwdriver. In this new area avoid the guards and you should read every note you find and interact with everything you find. The elevator is the end of the existing content. Have fun.
[Table created with Cheat Engine 7.4]
Edit:
I thought everyone knew about Cheat Engine. But I'm happy to help.
(The 'school_of_666-Win64-Shipping.CT' file inside the zip file is called (CE) table.
Password: f95zone.to