Yes, 英雄之戰:勇者無敵大冒險 is completely free and it doesn't have any in-app purchases or subscriptions.
Not enough reviews to make a reliable assessment. The app needs more user feedback.
英雄之戰:勇者無敵大冒險 is free.
To get estimated revenue of 英雄之戰:勇者無敵大冒險 app and other AppStore insights you can sign up to AppTail Mobile Analytics Platform.