Unfortunately, the official answer from Yahoo is that if you forgot your secret questions you will need to create a new account.
From Yahoo: http://help.yahoo.com/l/us/yahoo/edit/id_password/edit-20.html
You can get a new password, a Yahoo! ID reminder, or both. If you forgot your Yahoo! ID or password, go to the Sign-in Problems
If you forgot your Yahoo! ID, you need to provide three pieces of information so we can confirm your identity:
- Your birthday
- Your ZIP or postal code (at the time you created your Yahoo! account or when you last updated it)
- Your alternate email address -Note: You must have access to this email address
- Country code (at the time you created your Yahoo! account or when you last updated it)
Be sure to provide the same information you gave the last time you
registered for a new Yahoo! ID or password or the last time you updated
If you forgot your password, you can create a new one. But first
you'll have to provide the following information so we can confirm your
- Your Yahoo! ID
- Alternate email address, mobile phone number, or the answers to your secret questions
A Reset Your Password link will be sent to your alternate email address. Click the link and enter your new password in the Reset your password
If you entered your secret question incorrectly or forgot what you
originally entered, for security reasons, we cannot tell you what your
Yahoo! ID is or let you create a new password.
Please let me know if I can help you further.