Very old Hotmail account

I created a @HOTmail.com account back in 2004. Then around 2007 (don't remember the exact year) I created an @Outlook.com account.
I created it not because I wanted to create an @Outlook account, but the news spin back in that day coming from non-MS sources were saying you need to prepare ahead for the fate of Hotmail.

Approx around this 3 year period, MS emailed me (yes it was really Microsoft ) asking me if I wanted to set up another email address associated with a Hotmail account. I remember Microsoft provided the instructions and even the user name that I had to use. I remember the process was somewhat lengthy but I don't remember for certain if they ever used the term "alias" back in that day.

Two data breaches occurred with the original hotmail email address. This is one with the user name I created when I originally set up a hotmail account in 2004.

No data breaches have occurred with the other hotmail email address.

Could it be possible these are two hotmail accounts?
If they could be, what's a way to tell?
I like to be able to tell because if they're two accounts, I'd consider deleting the one hotmail account that was breached

Do you mean a way to tell if these are two Hotmail accounts would be if I'm able to log out of Outlook.com with one Hotmail email address and log into Outlook.com with the other Hotmail email address?

It would be helpful to know if my second email address was an actual MS account grandfathered, and not an alias created.

Actually, Outlook 2003 was the client being used back then with username@Hotmail.com

I've not known an alias was used, both my Hotmail and Outlook.com are actual addresses/accounts.

This is simple and yet complex because of the evolution Hotmail email service went through.

I have an Outlook account. Therefore I have a Microsoft account. i.e, Outlook email = MS account.

Isn't what was once Hotmail (regardless of any of its previous names) now Outlook.com ?

Today, with the new Outlook.com, when I attempt to sign in to www.outlook.live.com using username1@hotmail.com, it isn’t recognized. Possibly because MS allows only to choose one primary account to sign in at any time? So it allows me to sign in with username@Outlook.com. And if I changed username@outlook to username1@hotmail.com as the primary account, I should be able to sign in then?

To tell whether (username2@hotmail.com email address) is an an additional MS account, if I were to change the primary to the username2@hotmail.com email address, logged out, and tried to sign in with it, then if I was not allowed to sign in, would this indicate it's an alias, which MS does not allow you to to sign-in with ?

Could I potentially 'lock' myself out doing this?