Verified answer

You already own the copyright. You just need to be able to prove that the image is indeed yours should you ever end up in a courtroom because some nicked it.

They are already copyright. You can sign your photos in the lower right or left corner using permanent ink, or you can stamp the back of them with your name and contact information. I just sign mine on the image, and that's what most of the artists and photographers I have known do.

Yes because if they make a substantial amount of money you could recieve a portion of it.