I can't download Moocha and Finn's routes on the itch.io app. is that normal?
it only works with the demo
The game isn't out yet. You can get beta/early access (which only has the two routes so far) if you paid more than $45 USD, but if you paid the regular price of S29.99 USD, you only get the pre-order, and will get access to the game when it comes out only.
Did you only pay for the base (pre-order) game perhaps?