Can’t find out “confirmation code” and password has been reset

I created this new account so I could make a forum post and hopefully get some help. Here is my problem:

Last time I logged in on battle net was probably 2017 (at least that’s the newest replay in StarCraft 2 I can find and when I can find the newest World of Warcraft screenshot), and when I tried to log in to battle net sometime ago, it told me it will send a security code, or whatever it called it, to my e-mail. That’s a problem because I haven’t used said e-mail in YEARS, I just haven’t changed my Burning Crusade old e-mail (used on battle net and World of Warcraft) to my new e-mail for whatever reason. I’m not sure what e-mail service (or whatever you call it?) it was as it isn’t one that has like a website name in it (e.g. gmail or hotmail). Battle net has never asked me to write a security code sent via e-mail before (at least not from what I can remember), probably because I used to play Blizzard games very often in the past.

After trying out some things, it now also says my password is wrong even though I could use it to log into offline mode and play StarCraft 2 and its expansions offline that way, and another thing that confirms it is the right password is that I wrote it down years ago, just like I have done with my other various passwords. Copy-pasting should work as it did before it told me it was wrong, yet it doesn’t work anymore. I’m assuming the “wrong password” problem here is due to a security measure, not unlike how phones only allows you to write a wrong password two times, and locks the phone after 3rd wrong attempt. Except here it’s because I haven’t logged in “properly”. So now I can’t seem to log in to offline mode either.

What can I do? What info / proof do I need to provide to retrieve my old account? Is asking my family about my “childhood e-mail” the only option left to me?

I have tried searching for other forum posts, but couldn’t find the same problem. Sorry if it turns out I’m just bad at searching. I hope I’m posting in the right forum as well, as I’m not sure if I have used the forums before for anything, and I tend to be bad at forums for some reason.