Who knows. It doesn't matter.
17 USC 102 lists the kinds of things protectable by copyright under US law. These are:
(1) literary works;
(2) musical works, including any accompanying words;
(3) dramatic works, including any accompanying music;
(4) pantomimes and choreographic works;
(5) pictorial, graphic, and sculptural works;
(6) motion pictures and other audiovisual works;
(7) sound recordings; and
(8) architectural works.
A landscape feature is none of these and is not subject to copyright protection under US law, nor I think under the law of any other country. The "copyright notice" has no legal effect.
- 17 USC 120 Specifically prohibits copyright being used to prevent the taking of pictures of a building from a public place. In many countries Freedom of panorama (FOP) specifically permits publication of photos taken from public places. Se also this article on FOP. FOP is an exception to copyright protection, which applies to copyrighted architectural works and publicly posted works of art, such as sculptures. Since landscape features are not copyrightable at all, FOP does not strictly apply to them, but all the arguments for FOP would apply to them even more strongly.
In US Law, particularly under the Fiest vs Rural case, only works with original content, created by a person, are protected by copyright. (Other countries generally have similar limits on copyright.) But a feature of the landscape is not the original creation of any person. (If someone carved the landscape into a designed shape, it might be protect able as a sculpture.)
3 and 4. If it were a building, you could take pictures of it from a public place or a private place where you have a legal right to be, under 17 USC 120 . But since a part of the landscape is not protected by copyright at all, this is not really relevant.
- No under the US First amendment there is generally a right to say even false things. But if the landowner attempts to enforce this "copyright" it would be considered frivolous and any court proceeding would be promptly tossed out. The sign gives the landowner no rights s/he would not otherwise have.