Yes, it is very easy to unrelease a quest game.
I explained the gist of it here:
essentially quest files are actually just zip files, however if you extract the game files from the quest file you’re left with a published version that cannot be edited, this is purely due to the template/include information at the very top.
as such editing the code in notepad and deleting the include information will make it so the quest game editor will open the game as if it wasn’t yet published and all the handy quest editor tools will be exactly as they were for the author right before they hit publish.
I’m too lazy to explain it again right now, if you can’t figure it out based on my explanation in another thread, I’ll try and explain it better in a reply later.