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Training

to display the command bar: Ctrl+9
to display the classic menu: type MENUBAR and 1 (or 0 to hide it)
to display the lay out and model tabs at the bottom of the drawing: Tools > Options > Display > Layout Elements: check Display Layout and Model tabs
to file dialog boxes FILEDIA and set to '1 (or 0 to hide it)
to command dialog boxes CMDDIA and set to '1 (or 0 to hide it)
if a dialog does not appear in most o cases this is due by the offset of the screen of the dialog box. Press alt+space bar then M you will be able to use the arrow to put the dialog box in the middle of the screen.
to remove palettes Tools > Palettes > uncheck Ribbon