Thank you for posting question in Microsoft Q&A.
To delete and clean up the B2C tenant you need to have access to B2C tenant. Without access to B2C tenant you cannot delete and clean up resources.
If you are only admin for your B2C tenant then you can follow below instructions to contact Microsoft data protection team.
If you are the only global admin on the account and are blocked entirely, you can reach out to the Azure Data Protection team to restore access. 866-807-5850
Also, for the future, you can create an emergency access account (break glass) in Azure AD. This account will help prevent being accidentally locked out of your Azure Active Directory (Azure AD) organization because you can't sign in for any reason.
https://docs.microsoft.com/en-us/azure/active-directory/roles/security-emergency-access
Some other support option include;
azcommunity@microsoft.com
or creating a ticket through a different account: https://learn.microsoft.com/en-us/microsoft-365/admin/get-help-support?view=o365-worldwide#phone-support
Let me know if you have any further questions.
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