Reset my Apple ID security questions

See Here > Apple ID: Contacting Apple for help with Apple ID account security

Ask to speak with the Account Security Team...

Or Email Here > Apple Support iTunes Store Contact

Amber Syuan Guo wrote:

I wanted to reset my Apple ID security questions and asked to send reset email to my Apple ID email,

You need a Rescue Email set up BEFORE you forget the questions/answers.

how do you know if the correct rescue email is set up?

If you can't remember your answers to the questions then the only way to be sure is if you receive the reset email to the account that you think it's set to - if you can't find the email in either its inbox or spam folder then contact Support in your country to get the questions reset via the first link in AnaMusic's reply above, or via the form if your country isn't on that page.

When they've been reset you can then check and/or update your rescue email address via the Password & Security section of your account on http://appleid.apple.com : Manage your Apple ID primary, rescue, alternate, and notification email addresses - Apple Support