Could steam delete games?...

no

if you reinstall steam, the f2p games will go away from your library.

your stats are still saved.

yes, if you contect the Steam support.

Ask Steam support, they will do it but you won't get anything (gifts in you inventory) and I think F2P games are automatically removed from you account when you uninstall them.

Anybody else?

i believe if you ask steam support nicely, they will remove them.

Yes they will. I've done this. Usually takes a while though because steam support is pretty shitty, but they will eventually remove it.

They can delete games from your library, but they can't give you the key unused/new key.

100% yes

Steam can do everything.

I'd love to get rid of Betas from my list!!

They will remove it, just quote them their own TOS and they will comply

B. Termination by You.

You may cancel your Account at any time. You may cease use of a Subscription at any time or, if you choose, you may request that we terminate your access to a Subscription. However, Subscriptions are not transferable, and even if your access to a Subscription for a particular game or application is terminated, the original activation key will not be able to be registered to any other account, even if the game or application was purchased in a retail store. Access to Subscriptions purchased as a part of a pack or bundle cannot be terminated individually, termination of access to one game within the bundle will result in termination of access to all games purchased in the pack will be removed from the account. Your cancellation of an Account, or your cessation of use of any Subscription or request that access to a Subscription be terminated, will not entitle you to any refund, including of any Subscription fees. Valve reserves the right to collect fees, surcharges or costs incurred prior to the cancellation of your Account or termination of your access to a particular Subscription. In addition, you are responsible for any charges incurred to third-party vendors or content providers before your cancellation.

im sure theyll take anything you ask them too.

Write to Support.

Here is a reply for my request (removing a region locked game):

"Thank you for contacting Steam Support.

I can assist you in permanently removing the game(s) from your account. However, the game(s) will not be refunded and will not be accessible for future use.

Please note, any bans incurred in a game you are asking to be removed will remain on your account. The VAC ban applies to your Steam account, not the game itself.

If you wish to play the games again you will need to repurchase them from the Steam store in the future.

Additionally, if a game is removed and re-purchased, your Steam account will receive the same CD Key it was initially assigned.

If you registered a game with a CD Key and we remove it, the CD Key will no longer be valid and it will not be redeemable in the future.

If any game that you would like to have removed was part of a game package, it can not be removed individually. If you would still like a game from a package removed, please provide the name of the package in which you obtained this title.

Please let me know if you would like to proceed with the removal of your game(s).
"