if i get a discount on a game with xbox game pass will i still be able to play it after the ...

Yes. Anything you actually pay for, you get to keep.

You keep any game you paid for off of the game pass, but if you downloaded a game that was FREE with the game pass you wont be able to play it once the game pass expires.

So just to check what you are saying in regards to the discount, would I have been able to buy the game discounted while it was still on game pass, but because it had just left there was no discount?

Yes, the game still has to be on Game Pass in order to have a discount.

You must actually purchase the game and it’s normally offered at a discounted price for Game Pass subscribers.

I found this information on the
Game Pass FAQ page:

• Can I still play games after they leave Game Pass?
  
  Games you install using Xbox Game Pass remain playable once they’ve left the Game Pass catalog only when you buy them—and you get a hefty discount when you buy games as an Xbox Game Pass subscriber.
  
  When you buy games at a discount, those games are yours to keep. Similarly, any add-ons you buy are yours to keep, whether you buy the base game or not.
  
  Either way, whenever you sign in to Xbox Live, your game data gets saved online. That means, whenever you next play the game—if you buy it, if you play it at someone else’s house, or if it comes back to Game Pass—you’ll be able to pick up right where you
  left off.
  
• 
  

Dear Oofoofyey,

Find the answer.

• Can I still play games after they leave Game Pass?
  
  Games you install using Xbox Game Pass remain playable once they’ve left the Game Pass catalog only when you buy them—and you get a hefty discount when you buy games as an Xbox Game Pass subscriber.
  
  When you buy games at a discount, those games are yours to keep. Similarly, any add-ons you buy are yours to keep, whether you buy the base game or not.
  
  Either way, whenever you sign in to Xbox Live, your game data gets saved online. That means, whenever you next play the game—if you buy it, if you play it at someone else’s house, or if it comes back to Game Pass—you’ll be able to pick up right where you
  left off.