How to always print submenus from menu module?
One of the solution is to use Menu Block. It allow you to display any menu items based on depth. So you have all the control. To list all the menus, in Menu Block you can change the "Maximum depth" to Unlimited.


--- Updated 07/06/15 10:25am ---

You may need to use the Advanced options in your situation. Then check the "Expand all children of this tree". See below screenshot for details.