7. what are two different stock image licenses? how are they
different?

The two main types are Royalty Free and Rights Managed.

Rights-Managed: The buyer pays a licensing fee in order to be able to use the image. That licensing fee is based on usage. For example: location, type of media, length of time the photo will be used, etc. The buyer can also opt to pay for exclusive rights and there can be restrictions that apply based on all of the above factors.

Royalty-Free: A one-off fee is paid to the photographer by the image-buyer, but the photographer is free to sell that image multiple times to different buyers as much as he or she wants.  Essentially, this is also known as “unrestricted” content. The price for the image is often dependent on the image size (high- or low-resolution). The buyer gets no exclusivity to the image and the photographer might not know when, for what, and for how long the image is used for.

relief sculpture - images are set against a flat background.

a coin is a good example: the inscription, the date, and the figure are slightly raised above a flat surface. the ancient egyptians sometimes carved figures into a flat surface.  

pro: they take significantly less time to make and do not require as much tools or skills as free-standing

cons: not nearly as realistic, as it is not fully 3-d, and does not have the details that a free-standing one does.

freestanding sculptures (also called  carved in the round) are not attached to any  background.   they are 3-dimensional  and fully rendered.