Managing personal Outlook.com account settings, security, and privacy
Hey there! Nice to meet you!
Please be advised that Microsoft Support will not be able to assist you with manual recovery, unblock, and escalation for this case, as stated in this article, that they are not permitted to send password resets, access, or even change any details on the account: https://support.microsoft.com/account-billing/help-with-the-microsoft-account-recovery-form-b19c02d1-a782-dee6-93c3-dc8113b20c42
The only way to recover a hacked account is through the official Microsoft troubleshooter guide:
But since you mentioned that the security info has been replaced by the hacker, I'm afraid there is no other working method to recover the Microsoft account, and Microsoft Support cannot help either.
Thank you for your understanding.
Best regards,
Darhyl