Showing content of subterm under parent term I have following taxonomy structure  

parent-A
    subterm-1
        sub-subterm-a
        sub-subterm-b
    subterm-2


how can I show contents of both the sub-subterm (a and b) when i select/click subterm-1 ; and contents from subterm-1 (sub-subterm a+b) and from subterm-2 when I select parent-A      using views - block display
This may not be the most standard way of achieving it but it may help in your case. 
Just try the following code by replacing 24 with a $termid that exists in your case. And see if this gets your work done.

    //to get the children of a taxonomy term
    //lets take 24 for example 

      $terms = taxonomy_get_children('24');

      //to get the nodes associated with a termid

     foreach ($terms as $term) {
         $termnodes = taxonomy_select_nodes($term-&gt;tid);

         foreach ($termnodes as $termnode) {
              $node = node_load($termnode);
              $node_output = node_view($node);
              print render($node_output, $view_mode = 'teaser'));
        }
  }