As I said, it only asked if I was over 18. I am from NY. It accepted my entry after asking me if I was over 18. The wording you guys read at Amazon sort of says that, but in high school dropout fashion. They need to reword it.
Any Amazon URL ending with "-20" is an Amazon Associates link. It just means that Amazon will pay a percentage to their user named "spoofee" if you buy anything after using that link to go the site.
None of the info you enter goes to that user. But if it makes you uncomfortable, just copy the URL, paste it into the address bar, and delete everything from the question mark to the end before you hit enter.