You will need to first gain access to the parental account in order for you to be able to successfully agree to the terms and conditions. You won't be able to change the parental e-mail without being able to login to the prior e-mail that's listed.
The parent must agree to the new terms first and then you can login to your own account and accept them. If you don't have access to the parental account you will need to try to reset the password found here.
If that doesn't work try to fill out the Microsoft Account Recovery form found here.
If you're unable to either of those things then you may be out of luck. You can try to contact phone support and see if they are able to assist you in
Further information in regards to the new terms of service agreement update can be found here.
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