Managing personal Outlook.com account settings, security, and privacy
@Abdallah Makkawi said
Is the old Hotmail address permanently reserved ... is there any way Microsoft can restore or reattach it to my current account?
The whole Hotmail domain has been changed to a "Reserved Domain". Microsoft will not allow you to create a new account or alias with a Hotmail domain. I'm sorry but you can't get the old Hotmail address back.
https://learn.microsoft.com/en-us/answers/questions/5914862/reserved-domain-error
if an alias from a Microsoft domain, such as @hotmail.com, @live.com, @outlook.com, or @msn.com, is removed, it is permanently deleted and cannot be associated with any Microsoft account again.