May I get a refund?
“All sales and rentals of products are final. Prices for products offered via the Services may change at any time, and the Services do not provide price protection or refunds in the event of a price reduction or promotional offering. If a product becomes unavailable following a transaction buy prior to download, your sole remedy is a refund. If technical problems prevent or unreasonably delay delivery of your product, your exclusive and sole remedy is either replacement or refund of the price paid, as determined by Apple®.”
Please contact the App Store℠ to file any requests for a refund. See more here.
How do I re-download my purchase at no cost?
So long as an application is registered as being sold to a specific iTunes® account, that account can request a new download at any time. An Apple® Knowledge Base article describes this process. See more here.
How do I resume interrupted iTunes Store® downloads?
When the download of a purchased app, song, video, or game is interrupted, iTunes® will prompt you to resume your download the next time you open the application. See more here.