I have credit available on my existing apple account and wanted to gift an app to someone else. Is it possible to have the amount of the gifted app deducted from my existing credit available, or will it be charged to my payment info on file?
Sorry, but you cannot. A credit balance from an iTunes gift card or gift certificate cannot be used to purchase other gifts. You'll have to have a credit card on file in your account, and the cost of the gifts will be charged to that card.