Sorry to hear about the trouble you have been having. We are unable to help with account related issues here, but we are happy to point you in the right direction.

For sign-in issues, you can use our automated password recovery system at any time for no charge. See https://help.yahoo.com/kb/account/fix-problems-signing-yahoo-account-sln2051.html?impressions=true for more info.

Regards,
Yahoo App Support