Using theme regions from .tpl.php file I have defined many regions in my theme template. I would like to have a home page that uses these regions ... how can i use them? 
I have made a home.tpl.php but i don't know how to assign code to regions ... is it possible to do it even outside the page.tpl.php?
If you define a region you would normally then do the following in your page.tpl.php file...

&lt;?php if ($YOUR_REGION): ?&gt;
    &lt;?php print $YOUR_REGION; ?&gt;
&lt;?php endif; ?&gt;


You should have some similar examples setup already especially if you are using a theme that ships with Drupal.

You can create specific page templates...

function YOURTHEME_preprocess_page(&amp;$variables) {
  if (arg(0) == 'my_page') {
    $variables['template_file'] = 'page-my_page';
  }
}


Template suggestions

See: http://drupal.org/node/1089642

Context module

Also, the Context module is brilliant for this sort of thing if you intend on having different regions for different pages you can use Context layout.

http://drupal.org/project/context