Override a node page using page manager
Yes it is possible to use only context module to override layout.


When you first add context @ admin/structure/context/add, you need to select condition as "path" and reaction can be whatever you want. For ex. choose reaction as "Regions" and then go ahead disable region for the sleected "path" (the one you chose above in condition).


Just remember context module will use your existing theme layout and regions (.tpl.php files) unlike in panels where it allows you create your own regions and layout.