Deleted

i'm on my phone so can't check, but I am 100% sure you can delete games from your account through steam support, I know I definitely done it
edit: go to support, games & software, find the game you want deleted, find the option " I want to permanently delete X from my account"
source: https://www.pcworld.com/article/3012199/steam-makes-it-easier-to-permanently-remove-games-from-your-account-heres-how.html

Nope. You can add the games to the hidden section of your library, or use the support page to hide them even from the hidden games list, but you can't wipe out the license completely.

Yes you can, see jaaydee's response above. You can request a game removal from your Library through Support.

Sooooo, why would you want to do that anyway?
There are apps that you can reset your achievements back to zero if that's what you want...