Entities within a figure cannot be revised unless they have first been exploded. Figures are placed on an override layer when they are inserted into the drawing. Once exploded, individual entities of the figure can be revised using any of the above methods.
To explode a figure, select the Explode objects into individual lines and arcs tool from the Edit toolbox. Click on the figure to select it and then right-click. Now individual pieces of the figure can be selected for revision.