The OS itself provides the client with an API containing simple information about whether the user is an adult or a minor. It is also possible to have a require

The OS itself provides the client with an API containing simple information about whether the user is an adult or a minor. It is also possible to have a requirement from TPM. The age is specified by the administrator. It is possible to come up with some kind of state ID signature in TPM. The programs themselves have no way of finding out more.