I'm sorry to hear about the situation you're in. It sounds like you've accidentally locked yourself out of your Microsoft 365 Dev tenant and cannot access it because you don't have any phish-resistant MFA tokens registered.
You'll need to contact Microsoft support for assistance to get a solution to this issue. They should be able to help you reset your MFA tokens and regain access to your tenant. It's also possible that they may be able to help you delete the tenant and start over with a new one, although this will depend on the specific policies and procedures in place for Dev tenants.
To contact Microsoft support, you can visit the Microsoft support website and select the appropriate product (Microsoft 365) and issue (account and billing). From there, you'll be able to follow the prompts to get in touch with a support representative who can assist you.
I hope this helps. Let me know if you have any other questions.