The new version costs $20 and we immediately put a 50% discount on it. To get such an update, you have to spend not $5, but $10. After a while the game will cost $10 instead of $20. The discount will remain 50%. I hope I explained clearly)
Steam is no different from Itch. The game there will be sold in the same way as it is here. But there is an advantage on itch, here you can get the game much earlier than on Steam.
There will be no demo version on itche. There is a free version, in which there is much more content than in the steam demo version.