Hi,
I don't see any drifts in this thread that takes any of the answers away from the basic Question.
LeonieDF lists two Links and also mentions about having access to an account in the First place
See the Apple ID FAQ: Frequently asked Questions about Apple ID http://support.apple.com/kb/HE37, the section about Can I change the answers to the security questions for my Apple ID?
Now that you have a valid password it should be possible to reset the security questions.
As I have actually used that Method I later posted pics
https://discussions.apple.com/thread/3931778?answerId=18536783022#18536783022
Along with the pics I posted a second link to a site where you can change the Email (Rather than the ID) that gets used from Discussions, iTunes and in fact anywhere at apple that sends you email.
Changing Email if you can login to your Account.
Start with Logging in here
Once you have logged in there are several Edit Points down the left hand side.
Edit only the Email to make anything you want to come from Apple arrive at the email you are using currently.
I used this method as My Apple ID is also linked to iTunes and to Posting here at Apple Support Communities but there have been changes to the Account as I linked it to a iCloud ID as well.
This last bit stops you changing the Apple ID (normally based on an email) to something else.
This may work if you can't access the account On line and the email that the ID is based on is one you no longer use.
I also posted a Link to another thread where someone had used a Different method and had someone at iTunes Support help them out.
IN another thread felixjuls03 had contact with the iTunes Support people
https://discussions.apple.com/thread/3939171?answerId=18382647022#18382647022
Which seemed to help with App store or iTunes issues.
The presumption is with the answers here that as you can post and possibly "see" in the iTunes Store then the basics of your account work as far as a password at least.
From there you can access the Apple ID Support site an "Manage" your account.
This logs you in as you use your Password.
I have tested several Apple IDs I have with less questions set and have found that once I am in the First Page ( pic I posted ) then I can access the second as it is a menu item.
As the Pic shows it displays the Questions set for that account.
They are drop down and another question can be selected (And Answered and Saved).
Not counting the live Skitch link there are 6 others prior to this post.
Two of those are the Apple Info Doc and a link/expansion on that page.
One is to another link to another Discussion here at Apple Support communities.
That still leaves at least a couple more you could have followed which leaves us guessing as to which page you went to and why you are being asked to change questions first.
8:06 PM Thursday; June 28, 2012
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