Age Signals: how do you register an app ID, and do unregistered Win32 apps still run?

These two pages do not answer the questions below:

https://learn.microsoft.com/en-us/windows/apps/develop/security/age-signals/

https://learn.microsoft.com/en-us/windows/apps/develop/security/age-signals/implement-age-signals

They only show how a packaged, Digital Safety–registered app can ask Windows for an age band and a verified flag. Missing from the docs: how a developer actually gets that identity so the app is compliant; where you register; what counts as the app ID (package family name, Authenticode, sparse package, Store listing, file hash); and whether unpackaged Win32, sideloaded EXEs, Steam/Epic/GOG titles, portable tools, foreign publishers, or games built in Unity, Unreal, Godot, GameMaker, and similar engines can enroll at all. Also missing: if an app or game never registers or calls the API, does it still run as today, or will Windows restrict it? Is there a shim, a real 18+ override after the user verifies, or Group Policy so existing paid and line-of-business software is not stranded? Please add the registration steps and state whether this is opt-in for registered apps only, or an OS gate on unidentified software.