First off, the diameter symbol is not missing in the position callout for the slot C. See fig. 7-34 in Y14.5-2009 and para. 7.4.5.1(c) - last two sentences in this paragraph in particular.
Also, fig. 7-34 shows how exactly the tolerance zone looks like, so I think this will answer your both questions.
Side note 1: If the width of the slot (9.65+/-0.15) is the datum feature for stopping rotation, then the datum feature C symbol, as shown, has been put in wrong place. It should be in line with one of the dimension lines of the dim. 9.65, or should simply replace one of the dimension arrows.
Side note 2: If you work to Y14.5M-1994, the same concept (with some minor modifications) is covered by para. 5.10.1(c) and fig. 5-47.
Side note 3: I see that you also posted this question on another forum where you were told that the presence of the diameter symbol inside the position callout for the slot would be okay. Well, it does not work that way. You can't just "reduce" both center planes derived from width and length of the slot down to a point or axis (as someone suggested) and check whether this point or axis falls within cylindrical tolerance zone, because then you will not be controlling orientation of the slot relative to the higher order of precedence datum axis B. In other words the actual slot will be absolutely free to rotate 360 degrees about its true position (which by the way also looks to be defined incorrectly on you print, because x=60 coordinate is not basic), thus be not fully defined.