Can you please give me a list of my old gamertags

You could try contacting support to see if they have that information, but we wouldn't have that information on the forums as we don't have access to your account. http://support.xbox.com/contact-us

If you signed in and it showed a default gamertag and no score that means the email you used to sign in was not the email on the old account.

With that being said if you are not sure of the email on the old account but know the gamertag you can contact xbox support by going to support.xbox.com/contact-us and give them your old gamertag and if they can verify ownership of the account they can give
you the email thats associated with that gamertag

It doesn't give me that option to unregister since i'm on a new account and don't have access to the old gamertag. I've tried to enroll the new account and it tells me that console is registered to a different gamertag (my old gamertag)

Sorry to hear it. If the content is not listed in your download history then it's possible that it was added to a different account. Can you please check other gamertags you may have on the new console or the old one?

I mistakenly used an edit, and now I can no longer edit my gamertag. When I try to edit it for a fee, it gives me an error. If possible, could you manually edit it to "*****834" for me?

Please assist me with editing my gamertag.