Unfortunately, if, when you created the account, you have not registered a secret question which you remember, or an alternate recovery email address or phone number to which you have access to receive a reset code, you cannot prove that you are the account's legitimate owner. Hence account recovery is absolutely impossible and there is no way around it.
Go to this page
http://io.help.yahoo.com/contact/index?locale=en_CA&y=PROD_ACCT&page=contact Select password and sign in
Select forgot password
Click on "password helper" or
Click on the envelope to get the Yahoo customer service phone number for your region.
This number no longer works as of March 2015 Or click on the envelope to open an e-mail case. If you do not know your security question, in the space provided for them, write "unknown"