I do not know my Yahoo password to both my Yahoo emails and my alternative email, but I do know my security question. When I access the recovery page, it doesn't give me the option to use the security questions.
According to Yahoo help, if you have alternate emails set up, the Security Questions might not be available right away. You will have to try a few times using the email address and then the option should be available. While you use the Forgot Password option, the account might get blocked due to the failed attempts. But try again in 24 hours and you should be able to try again. After 24 hours, use the Forgot Password option using the following link: https://edit.yahoo.com/forgotroot/