Finding hooks Wordpress

I know there are lists of hooks for WordPress like --> http://ift.tt/1f1lEM7

But if I want to find hooks for a plugin like WC Vendors there is a much shorter list of hooks on their website.

Are 'do_action' and 'apply filter' functions the only thing we can modify? If given a class like --> http://ift.tt/1IFo2o7, is there any way to modify it?

Are we limited to the do_action hooks or is there a way to modify other areas as well? Can we use the WordPress hooks to hook into the WC Vendors plugin as well?

via Chebli Mohamed