Copyright licenses can be constructed in virtually any way that complies with contract law including (but not limited to)...
per use basis
timed license
flat rate
exclusive use
or any combination thereof.
Different uses also have different licenses, often specifically corresponding with one of the exclusive rights of the copyright holder. The right to perform or display, for example, would roughly align with a performance license.
There's really just the one. There are many, many different licenses, though.
from copyright clearance center
Yes; but the vast majority of uses would require licenses from the copyright holders.
Public domain images have no copyright restrictions.Creative Commons images are protected by copyright, but have extremely broad licenses.
Yes; most licenses are non-exclusive, limited, and revocable.
You would need to go directly to the rightsholders individually.
Copyright protected or trademark images, such as cartoon characters, require licenses from their owners.
Yes, often more than one for each book.
No, they only monitor the licenses that come through them.
Yes; reusing others' content requires their permission. Depending on the song and the type of use, you may need licenses from many different stakeholders.
No, using a cover of a song without copyright for your own performance or recording is not allowed without obtaining the necessary permissions or licenses from the original copyright holder.
License art? If you mean a copyright, you have that for anything you make. If you mean to sign a contract and sell copyright licenses, you have to be 18, or your parents have to sign the agreement.