theme individual block I looked over the theme suggestion but when tried with dummy text, the block doesn't show any dummy text. 

on view source, it showed "id=block-menu-menu-top-menu-navigation"

Tried naming block--top-menu-navigation.tpl.php and block--menu-menu-top-menu-navigation.tpl.php but dummy text still doesn't show up. 

Perhaps my naming the files is wrong?
The template file you have to create should be 

block--menu--menu-top-menu-navigation.tpl.php

Hope that helps.