Corrupted? How so? I didn't update the demo, I just changed it's name in itchio so it says "Demo" but I didn't touch the files themselves.... that's so weird I really have no idea how could that happen
It must be something specific like your windows version or something. I do have issues with games on itch occasionally, though, that appear to not be caused by the developer. I can only recommend downloading it again and attempting install on another corner of your PC. In a prenamed folder. AWAY from desktop. Sounds weird as hell, but mostly works.
I have! And I really couldn't find anything that could possibly be doing this! I'm so sorry my knowledge in coding and these type of technical issues don't go that far, seriously!...but I've tried to do some research on my own, I've seen some stuff that could be acting up on your computer because considering the great amount of people that have been able to play with no issues it's logical to consider that it's not exactly the game files themselves!....
So for what I've seen, it could be the typical issue with the antivirus/windows defender! Try disabling it and see if it works!
It also could be that if you're using the itchio desktop app, itch app is notorious for throwing TLS/network errors if local network settings or certificates are out of sync. Try to download the game directly through a standard web browser instead!
And other stuff that I've found I'd copy/paste it here textually:
It seems the download keeps dropping mid-way, the critical engine library librenpython.dll is either completely missing or only partially downloaded (0 KB), causing Windows to throw the "not designed to run on Windows or contains an error" message.
Try an alternate web browser or Incognito mode: If Google Chrome is consistently failing to retrieve the file, they should clear their browser cache, use an Incognito window, or try a completely different browser like Mozilla Firefox or Microsoft Edge.
Use a download manager: If their local internet connection drops frequently, a download manager tool can handle the intermittent packet loss and prevent the archive from corrupting before it finishes.
(For what I've seen, this is an issue that occurs specifically when you're in the process of the download.... I'm really really sorry I can't be of much help more than research myself and trying to help like this!)