Can the author of this theme to create a premuim version, I am willing to purchase it
 

I understand there is a way to pass the google mobile test, however, the performance is very sloppy can some people's phone may have hard time access to the site.

Is montezuma theme responsive? Is there a demo site I can take a look?

Yes Montezuma is a responsive theme. I'll send you a pm with a link to a live site.