Can dumb be cured by casting fog on yourself again?

Can frog be undone by casting frog on a player turned frog?

Finally, reviving a dead person... My white mage is the only one that knows Life & Heal. Life is at level 1, Heal is at level 3. Should I increase Heal to level 6 to use it for reviving characters? Is there any advantage to using 6MP vs 1MP? Maybe it works better during battle?