All members of the World Trade Organization recognize each other's copyrights.
Copyright is a federal law which would be valid in California.
No; protection is automatic and registration is not required.
Any owner of a copyright can sue for infringement as long as the copyright is still valid (i.e., for 95 years from publication).
Orphan works are works in which there IS a valid copyright but they holder of the copyright has not come forward or is not know. They are NOT available for reproduction.
Yes; it was fastidiously renewed and will be protected through 2056.
There are several copyrightable works by that title. The oldest, the song, will be protected through 2022.
Provided that all original documents and renewals were properly filed the copyright on Jerome Kerns music for Showboat would be valid until December 1st, 2015 (the end of the calendar year, 70 years past the death of Jerome Kern)
Public domain means not covered by a valid copyright, anyone can use such material anyway they want. If a copyright expires or becomes invalid for some reason the work enters the public domain.
The copyright date on something is when it was CREATED or first published, and the copyright lasts for about a hundred years after the author's death, so YES, anything with valid copyright date of 2002 or 1993 are till in effect. On the other hand, it is a good question whether a famous painting still has its own copyright and whether a photograph or digitization of that famous painting may have its OWN copyright dates, as derivative works of the original.
Everything is protected unless explicitly denied protection by law or court decision. Concert posters are perfectly valid as copyrightable works.
There is nothing that need to be done to "claim" a copyright. Copyright protection is free and automatic. All that is needed is that a work of sufficient originality is "fixed in a tangible medium, perceptible to human eye, machine reader or other device".
Statute of limitations apply to criminal or civil proceedings. They do not apply to intellectual property. However, in most cases the copyright is valid for 70 years after the death of the individual.