Suggestion for Xbox

https://xbox.uservoice.com/forums/363186--new-ideas

Then what's the point of security key?

For Xbox One this should work, but for the 360 there's simply not enough ram to run the game and an app side by side.

Yes it's called remote play

But still requires a console unlike xcloud

And a good connection

Playsstation and xbox both have it

But very limited

Xcloud has larger support

https://www.digitaltrends.com/gaming/xbox-game-streaming-how-to/

Its a bit dated but the steps are the same and ios is supported for xcloud

MS probably won't offer this because they want everyone to use Xbox Music.