Q: I recently changed my Apple ID username, now I need to change it back.  How can I do that?

You can't change your Apple ID, but you can start a new one.  And revert back to an old one.  Purchase and data are associated with each unique Apple ID so you may lose purchases and have to move data from on Apple ID to another if you have iCloud items like Photos in each ID.

If you need help reverting to the old Apple ID, let us know what devices you need to update....

That is not correct. You most certainly can change your Apple ID unless it is an Apple Domain email address like @me, @mac, or @iCloud.com

People change emails often, and they need to be able to change a non-Apple Apple ID to reflect their current email address. That is done via Manage your Apple ID.

Cheers,

GB

It is not clear what your issue is or what you have done.

When you say you recently changed your Apple ID username, what, exactly are you referring to and how did you go about doing it?

Cheers,

GB