Can’t buy Xbox 360 games/add-ons as gifts in the new store interface.

Xbox games do not support external mods or add-ons of any kind. If you can’t buy it in the store you can’t use it.

you would only be able to buy backwards compatible games on the Xbox one/series store. They do not go backwards to the 360.

You cannot buy games once the store has deactivated purchasing, or add new games to your account for 360 store

Unless you're trying to buy an Xbox 360 game or add on, then yes.

The store should give you the selection to use the funds on your account from the gift card first, and the rest from your credit card.

If you try to buy stuff on a real Xbox 360 console, you can also use your account credit from the gift card for your Xbox 360 game purchase. Just not on the Website or Xbox One console.

I still think there should be some way to allow microsoft ballaances to be allowed to buy backwards compatible games on xbox one instead of having to log on an actual xbox 360 and whatnot. Maybe they could make an app or program that launches the 360
marketplace. Instead of going to the xbox digital store this new store app would emulate the xbox 360 marketplace. The same way if you were to load a backwards compatible game but now you would be able to have one stop shopping and you could finally use
gift cards to buy xbox 360 games on your xbox one.

As far as I am aware, no Xbox One games are region, but Xbox 360 games can be. As long as game was not bought from Xbox Store using Buy as a gift option, it will work fine.