Can negating Donovan*** R: turn it off for the entirety of the turn? It's "Only playable once per turn," the same wording as Kyoshiro**, Dhalsim*, Ibuki** and some others, and once it has been played that restriction remains even if the specific text is negated {another way to look at it is, you play it once, the entire effect is negated, but if you attempt to play it again, the gamestate sees "This ability has already been played once this turn" and places the restriction}.
On the other hand, when the text reads "<E/F/R> <cost>: Once per turn... ." (promo Ukyo, Andrew Olexa, Akuma-6, Felicia-4, Will for the Fight, Seong-Mina-3, Twelve-1, the list goes on...) negating the ability will allow it to be played again during that turn -- because the entire ability, including "Once per turn," is negated and has no effect.
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