Hi. Despite what you might expect making the game free like this, the full game will only be downloadable during the sale (even for people who have claimed it for free). I can tell because if I hit download at the top of the game page after claiming, only the demo is available to download there.
Itch.io is strange with how it works when there's a free sale and there's also a demo available. It's not claim an be available to download forever like it is on Steam.
When there's a demo on the same game page as the full game (or any free files as far as I can tell), then when the game is "claimed" for free, as soon as the sale ends only the demo/free files can be downloaded. Even though it was "claimed."
The way to know what's going to be available to download after the sale ends, is to try downloading from the very top of the game page after claiming. Only what shows up when hitting "download" there is permanently "claimed" past the end of the free sale.
It's pretty dumb and confusing. And it must have made a ton of devs think they're giving something away permanently when really they're not.