I can't sign into 360 or backwards compatible One games

Hello, As long as the 360 game is backwards compatible you will be able to play it through the One console. When you try to play the 360 backwards compatible game it will sign your system in the 360 servers and you'll be able to play that game.

No. It's not compatible for either.

This is the official list for One backwards compatibility - https://www.xbox.com/en-US/xbox-one/backward-compatibility/available-games

I can't find the official page for the 360 at the moment, but this one is accurate - https://en.wikipedia.org/wiki/List_of_Xbox_games_compatible_with_Xbox_360

The "Backwards Compatibility" only exists for games that they have told the XBox ONE to recognise as "Backwards Compatible".

Most of the games on the XBox 360 simply will not work on the XBox ONE.

Microsoft will claim the reason they can't make everything available at once is that they need a Publisher's permission to make the game Backwards Compatible.

But the real reason Backwards Compatibility exists is to lure XBox 360 owners who have been on the fence for a while into the false supposition that they will be able to play their 360 games on the ONE.

If you could do that... why not buy a ONE?

The Xbox One is not backwards compatible with Xbox 360 games so you can't play any 360 games on the Xbox One

If it's backwards compatible it would only be available on the Xbox One as a backwards compatible game. Not on the 360

There are backwards compatible games available for the 360. Black is one of them.