So there's our misunderstanding. I skipped the tutorial, because I already saw your demo video. Then I clicked on the US on the map and played the first challenge called "Tutorial: Cipher salad". After that I always got the "Buy now" popup when I tried to play another challenge.
But you're right, the tutorial is playable too and it consists of the same kind of challenges, not just simple explanations how to play. So my initial statement was not correct.
I see. Well, I hope you can appreciate there are limits to what I can do – if someone skips the free challenges then is unhappy there aren't enough free challenges, I don't really know how I can fix that. If you want to go back to play the tutorial challenges, they remain available.