Wither Skull cannon

Hi I saw a video from HidDen about a wither skull cannon but I think the commands block are a bit different so I couldn't replicate it. So I saw the comments section and there was this discord link. If someone knows how to make the video works nowadays it would be really cool to know.
link video: https://www.youtube.com/watch?v=yEarKKcJw0o
Also if someone knows how to make via command block to an item throw snowballs when I left or right click it would be great too.