Menu and submenu

Can you please tell how menu and submenu should work with keyboard?
My understanding is :

*       when no menu is opened , Tabbing takes you across the menu items in the horizontal row

*       When one of the menu items has focus, pressing the Enter key, Spacebar  open the submenu

*       When Menu is opened (that has submenu), tab will close the existing submenu and restores the focus to ? ( the Parent menu item  or this show take focus to next menu / to the first item in the menu bar)

*       Up and Down arrow to navigate within the open submenu items

*       Pressing the Escape key closes the submenu and focus should be restore to parent menu item




Thanks
Siri