Can you get back old Hotmail account, after having renamed it to new Outlook account?

Well here is Microsoft's answer on Reddit!

If you renamed your account, and want to rename it back to the original name, you can do that.

IMPORTANT: This may not work if you are outside of the US and have a "@live.com" or "@Hotmail.com" address!

First, remove the alias that was created when you renamed your account (the alias will be for the original name).

Go to http://account.live.com, select "Notifications" then "manage your email preferences" and you'll find links to remove aliases.

Second, go back to the Rename page, Sign In and rename back to the original name.
Hope it helps someone!