Load page through ajax what are the options (all possible ways) to open a page through ajax in D7?, also can ctools module be useful in this?

if yes then can anyone provide an example hint using ctools.
Ctools give you a modal frame api as well as many different ajax helpers. This is probably your best bet for implementing AJAX in your site.

As for listing all possible ways there are loads, ranging from custom implementations to contrib modules, your best bet would be to search drupalmodules.com for potential candidates.