How can I tell?

Sounds like you are being scammed. You can check the status of the investigator's license here: https://search.dca.ca.gov/.

Can I own a copyright of a pattern or design on a plate?

If it is original and creative. Yes

Exposing?

Dial 9-1-1. Report the creep to the police for attempted extortion. Have him put in jail. Problem solved.

Is a royalty required to be paid to copyright holder for reproducing a popular music composition and changing the melody?

What you are proposing is called an "adaptation." There is no compulsory license for adaptations. The permission ("license") to make an adaptation...

If you own the copyright in the photo (either because it is a selfie or you acquire the copyright from the photographer) you can send a DMCA take...

Walking into a minefield of potential copyright and trademark infringement liability. The 'copyright specifics' of meme culture are that there are...

Unless you encourage viewers to download and save copies, it sounds like the illustration was merely displayed on your website. That it is...

How do companies like canvascultures.com and https://inktuitive.com reprint images from Disney, the Mononply game, and films?

They may or may not be licensed. If they are not licensed they are probably infringements. Noticed neither company shows a US address. If they are...

That doesn't sound right. Even in a 360 (publishing included) deal. Consult a music lawyer or Don Passman's book:...

Being subject to the laws and jurisdiction of the courts of California is generally a legal consequence of doing business here. If the legal wrong...