If a movie has been registered as www.movienamemovie.com And it ONLY registered a .com if I register a .net, .org, .info, etc. Would it be legal?
Depends. Is the name under trademark? Is your use a violation of that trademark? And more importantly, if they come after you, which they can do for any reason, are you prepared--financially--to mount a formidable legal defense?
If you just make a site with info about a movie and make clear it isnt the official site, then I think you wouldnt get much trouble...
I sometimes wish someone ought to post a sticky saying "registering the [ext] of this domain name is legal. How you'll use the domain name and what your intent is are another story." Shorthand is if someone can demonstrate trademark rights to the term/s that is/are in question, and you register a domain name that can possibly infringe that right, then expect trouble. There are other threads asking this very same question. I suggest you take some time to read some of them instead of being lazy.
Basically this come downs to what you are going to use the domain for. If you are purely registering the domain to profit of the movie hype then that would be a clear cut case of cybersquatting and you will lose the domain. The same goes if you have any content related to the film. That would be a trademark infringement and cybersquatting violation. Let's take an example: With Myspace.com you would be fine if you have a domain like my-space.com and you use the site as a personal blog talking about your life etc. However if you use the same domain with content related to Myspace.com (e.g. templates etc.) then that would be a trademark infringement and they can claim the domain from you.