Short of physically removing the device from the owner there is no tamper proof method, just varying degrees of effectiveness.
Please see the reply on your other thread, which also applies to home devices.
Otherwise use the access controls built into the BT Home hub.
They only work while connected to the home hub.
What if one didn’t need to remove the device from the owner or expect them to re-obtain it after having removed it from them. What if one could, for example, time-block/restrict a child’s phone remotely both initially at set-up and subsequent to setup thus limiting the chances of children finding ways to delete the restrictions?
Can the device access controls using the admin password be nullified by a child resetting the hub or in any other way?
And what about cellular network data?
Access to to the internet via a home hub can be time controlled via the home hub but this can be circumvented by simply factory resetting the hub to its default condition. As stated previously there is no such thing as tamper proof restriction unless physical access is prevented either access to the hub or access to the device.
As far as 4G data is concerned, I have no idea what is available in terms of access control, but again doubtful if there is anything fully tamper proof.