I'm Brazilian, I think you are too because the demo has the Portuguese option, but I'll write in English, if I change things in your demo, applying my ideas can I release it as a commercial game?
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Hello, as stated in the description, you can :) Just take a note on the sprites that I used for this project since I do not own any of them, if you're willing to use any of them please check the asset's page (All the links are in the description and also in the designated's folder).
Espero ter ajudado, qualquer coisa só comentar :)