Can I use a prepaid Visa gift card to open an iTunes account or pay for music on iTunes?
No, you cannot use any bank issued gift card (Visa, MasterCard, Discover, or American Express) to open an iTunes account or pay for music on the iTunes store. To open an iTunes account, you need one of the following: an iTunes gift card, a valid credit card, or a PayPal account. You can however use your prepaid Visa gift card or other bank issued gift card to buy an iTunes gift card from a retail store and use that to purchase music on the iTunes store.
Is a credit card required to purchase music on iTunes?
No, you do not need a credit card to purchase music on iTunes. You can use an iTunes gift card or a PayPal account connected to your bank account.
Can I redeem a US iTunes gift certificate or gift card if I live outside the US?
No, iTunes gift certificates and gift cards are valid for use only in the country in which they were purchased.
Source: Apple.com and Apple Customer Service