There's one more cell that can become red. I'm stuck there too, I can get 401 now but I still don't see how to get 405 in just three moves.
e: got it now, I forgot about keyboard movement.
There are only a few sensible options for where the 3-long piece can go. When you find the right one, at least a couple other pieces might fall into place when you think about the possibilities for a nearby endpoint. There are four L-shaped pieces, so you'll also need to think about all the places you can put them while still leaving room for all the other branching paths that are going to be necessary.
If you made it to this level without needing help, I'm confident you can get this one too. There's a solution in one of the videos below but I don't think you need it, if you feel like giving up then maybe come back later and give it a fresh try.
I had to turn the volume way up to hear the voices and even then they were still a little hard to understand sometimes, if it's possible to add subtitles they'd be helpful.
In my first session I gave up at the sliding puzzle because the controls didn't feel suited for it, there were lots of halting little motions and shelves constantly catching against each other instead of smooth slidng.
In my second session I somehow ended up clipping the piano through the locked door and ended up stuck.
Took a couple tries but I got all four endings, thanks fkchaud for mentioning the two I didn't get the first time (and for mentioning how to keep the wizard alive).
I encountered a couple minor bugs:
The most satisfying quest was giving Cpt Skelly their body, and I enjoyed all the little fun bits like the "do not open" chest and the normal cow. The most frustrating part was losing coins on every hard bump, especially if they land in ways that make them tricky to retrieve like in between characters and objects.