Yes, 算术大师 脑力训练 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.
算术大师 脑力训练 is free.
To get estimated revenue of 算术大师 脑力训练 app and other AppStore insights you can sign up to AppTail Mobile Analytics Platform.