Q: Gift card

Use it to purchase content

Or you could give iTunes content to another account as a gift.

http://support.apple.com/kb/HT2736

Rescue email address and how to reset Apple ID security questions

You cannot gift with a gift card balance.  You must use a credit card.

You can use the card.  Reset your security questions.  I gave you the link.

And we seriously want you to follow the Gnome's advice!

Go to https://getsupport.apple.com

Choose 'More Products & Services', then 'Apple ID'.

A new page will open.

Choose 'Other Apple ID Topics', then 'Forgotten Apple ID Security Questions'.

The article Gnome gave you explains that.  You have to be able to answer your security questions first, though.

You can edit or delete your rescue email address at My Apple ID. To edit your rescue email address:

1. Navigate to My Apple ID using your web browser.
2. Click "Manage your account"
3. When prompted, sign in using your Apple ID and password.
4. Click Password & Security
   
5. You'll be asked to answer 2 of your 3 security questions before you can make any modifications.

if you have never used the ITunes gift card, contact the iTunes department and they can de-activate the card for you, but if you have used any of the money they will not be able to do it, and you will need to get access of the account if you want to use that money.  TJBUSMC1973 had the right infomration to contact apple to have them reset your password.