How do i delete old questions on yahoo?

Once resolved or in voting you can't delete them.

To delete a question while it's still open, go to the question , pass your mouse over the pencil icon in the toolbar below your question, click Delete Question.

http://help.yahoo.com/kb/index?page=content&y=PROD...

All you can do is hope it is reported as a violatione even resolved questions can be removed that way.You could try emailing the YA team y_answrs_team@yahoo.com

explaining as to why it (they) should be deleted,. however Yahoo will only delete questions if they violate the community guidelines or reveal personal contact information (e.g. email address, phone numbers, address etc).

The same as above pretty much applies to your answers.

You can't. Once a question is resolved it becomes property of Y! and can only be deleted or removed by a Y! moderator.

You can't.

Only way is if yahoo decides to take it down due to violating their community guidelines