Backbone One (the controller) does not require the app to work and is great for players of all ages! The controller works inside any game that supports game controllers (Minecraft, Roblox, Apple Arcade games, etc.).
However, much like Google, Fortnite, Discord, Houseparty, and most other social apps, the Backbone App requires you to be 13 or older because of its social features like voice chat and messaging. Apple requires users to be 13 or older to use Sign In With Apple. Thirteen is also the minimum age to manage your own Google Account, and Children under 13 (or the applicable age in your country) whose accounts are managed with Family Link can't sign in to the Play Games app with their Google Account.
NOTE: Keep in mind that the Backbone One can be used on thousands of controller-compatible games without the app.