Do I have to buy madden separate for older gen or can I buy x series game and play on Xbox one

No you have to buy a cross gen or.an xbox one game or use xcloud with ultimate.

You can run next gen games on 12 year old hardware

Series x ijust 2 years old the cpu and gpu was released 2 months prior as it's new technology

Xbox one CPU was released 12 years ago and it was dated when released because it was based on existing tech

Like i said,it will only run on the current gen consoles,the Series X/S.

The older gen consoles don't have the hardware to run Starfield.

The Xbox One X is a last gen console.Skyrim works as it was made for the Xbox 360 & upgraded to run on Xbox One consoles.

If you want to play Starfield the4n you'll either need to buy a Xbox Series X or S or play it via the cloud if you can.

It's been known that Starfield will only play on current gen consoles for quite a while.

Because it's a Xbox Series X/S only game.

Older consoles can't play it due to technical limitations.

If you have Game Pass Ultimate you can play it via the Cloud if that's available in your region,if not then you'll have to buy a current gen console.

More & more games will be current gen only as time goes on.

All Xbox One games can be played on the Series S/X via backwards compatibility. Kind of like how you can play 360 games on the One now. You would be playing the One version of the games.

With Cross Gen Editions/Smart Delivery, you're buying the One version and get an upgrade to the Series S/X version of the game when you get the new console instead of having to buy the Series S/X version and you an take advantage of some of the upgraded
features.

Sorry but 2k has not announced cross-play for the game.

Since you have to pay for the game separately on both consoles I doubt they will have Xbox One and Xbox Series X crossplay.

Before someone says If you buy NBA 2K21 Mamba Forever Edition you get the Xbox Series X version. Yes, that edition bundles both the Xbox One version and the Xbox Series X version but is not a free upgrade or the same game.