Royalty Free is a type of license which is used by stock photography agencies to sell out the stock images. It means you have to pay for the license once, and then you can use it forever.
No, to buy an image you have to pay the price amount of the image.
Rights Managed Licensing allows the buyer to license an image for a certain use and specific time. Fees for RM images calculated by multiple factors which involve the nature of the intended use, geographic distribution, the term, media type, size of reproduction, and the size of the print run or distribution. Protected rights licensing may be provided for some RM images.
A copyright is a assignable legal right, which has given to a owner for some year to publish, print and etc.