Will gold subscription discounted games work after expiration?

Yes they will work after the subscription ends. If you payed for a game, then it's yours to play as long as you want, whether or not you payed full price or a sale price.

The sale btw is open to everyone including free/silver members from Tuesday.

It's holiday time and there are many game discounts. However, I see they all need Gold subscription for the discounts to apply. If I get the Gold subscription for a month and buy the games on discount will I be able to play them even after the gold
subscription ends?

I don't see why they shouldn't work, you've purchased the game.

I have done this in the past. You can play them, but cannot join in online multiplayer modes until you have gold again.

Yes, for sure. If you pay for them it doesn't matter if you got them on a discount or not. You own them and you will be able to play them. Enjoy your games!

Yes, if you buy it on the discount with game pass, you do keep the full game since you bought it - even after the game pass subscription expires.