You won't be able to change your rescue email address until you can answer your questions, if you don't have access to the email account that you currently have it set to then you will have to contact Support in your country to get the questions reset.
Contacting Apple about account security : Contact Apple for help with Apple ID account security
If your country isn't on that page then try this form and explain and see what they reply with : https://ssl.apple.com/emea/support/itunes/contact.html
When they've been reset you can then update your rescue email address for potential future use : Manage your Apple ID primary, rescue, alternate, and notification email addresses