Is it possible to change the location and size of the blocks/tabs in Drupal? This is my first time using Drupal. so I am not too familiar with it. My question is that is it possible to change the location, size etc. of blocks/tabs that are available as default through Drupal? The blocks/tabs I am talking about are shown in the following snapshot.
I assume, you are referring to "regions" as  "block/tabs". If that is the case, you can add/change the regions in your theme_name.info file and page.tpl.php file.

You may find this Link useful.