Create a new project, and transfer all of the data from the old demo file into the new project file. Everything will be there.
One downside, though, is that RPG Maker VX Ace will become stupid and won't let you view the graphics files. This has happened to me with some Ace games I downloaded. They let me check out the music used, but not the graphics. That may be your only problem, but you can easily get graphics back.
I would give this game a try, but the only download link I have found on this page is broken. Where can I download the demo? The main post should also describe the game more than like "Coming soon". If you have dropped the project, write that, do not leave everything without update, because it is disappointing.
At first, I was going to put player objectives on the screen labeling it as "Helpful voices"... But that's dumb, I have a madness system. It will simply whisper objectives.... I mean they're probably objectives. The voices wouldn't lie right? They're friendly, and ...helpful. So clearly you should do what they say. Just watch the dark corners of your screen for advice and it will all work out!