I have tried to block YouTube on the firewall so that no device can access YouTube on my WiFi as my kids are added cted to it but have also managed to see adult content on it I have noticed that the access to YouTube through browsers and been stopped but android app of YouTube is still able to get on, is there a way to stop this app and block it from access via WiFi
But that only works as long as the child doesn't change the DNS names that VM users because that is where the block is carried out and the connection is via VM's wifi. But you can be canny enough to disguise that fact from your offspring so they can't circumvent. And if you block this way you lose access to You Tube too , except on your VM TV service.
A cheap hub has very limited capability. However, something such as Google WiFi enables you to pause a device for whatever time period you choose, you can also create scheduled pauses for periods such as their bedtimes.