[Uploaded 2019/03/15 on YT]
This is my best solution so far for blocking YouTube both Web And Application for mobile devices. Most of the Internet Tutorials out there (On YT) is blocking only the "YouTube Website". And I NAILED IT by scanning DNS requests using a Third party app.
Hope I saved all of your bandwidth problems.
Used Router for the Demo:
Arris Model SBG6580-2 (Cable Internet)
Follow my Channel If you like :)