Playing Xbox 360 games on the One without a 360 account

The account on the xbox 360 and the xbox one are the same account, if you know the email address you may be able to recover the account. For this to happen you should be able to access that email account or know the security contacts you had for that
account. If you do not know that you maybe able to still recover the account using the form, but the less info you know the harder it becomes.

backward compatible game only use cloud storage that is synced on the Xbox one witch means if there is no profile connected the game will not be saved

so you will need to connect an Xbox live account (the one your currently using on your Xbox one should work)

also if you need to reset your password you should go here:

https://support.xbox.com/en-CA/my-account/microsoft-account/lost-password-solution

Is the game attached to your Xbox One account or a different account?

You can try and recover/reset the password for the account that you have forgotten the password to by going to

account.live.com/acsr and filling out the form there.

Do I have to have an Xbox 360 account to play Dark Souls 1 on Xbox One?

If yes, how can I create one without and Xbox 360?

Do I need to be connected to xbox live to play the game or can I play it offline?

1- you can't play the Xbox One games but the original 360 or Xbox games

2- for someone else to play the multiplayer pair without gold, you need to configure the gold account as the main one in the xbox where you will play and the other user without problems can play in another xbox