Just an FYI (maybe it's common knowledge), If you don't want to be bothered with the stupid age restriction bs on youtube. You can simply bypass it by removing the "watch?" piece of the url,, leave the "V", delete the "=" sign and replace with a forward slash "/" and hit enter and it should play.
https://www.youtube.com/watch?v=U3GA...U98QBCGVjDfQF4
to
https://www.youtube.com/v/U3GAcSr8Hw...U98QBCGVjDfQF4 (then enter)