Yup. Try it. Works on Android and Windows too.Seriously, does that work??
Yup, there are apps for that. They require root though.It just ocurred to me that Android is basically linux, and it prolly has etc/hosts file. If you were to inject some addresses into it, I'm sure it could be efficient at blocking youtube ads. Don't overdo it though, because it may very well slow down your phone. App for doing this at desktop PC's that I know of is called Hostsman.