If I move Yanmega from being an Active Pokemon to the Bench, and then back to Active again in the same turn, does it get the bonus damage?
Yes.
Surprise Strike


x2
-20
WindfallShuffle your hand into your deck. Then, draw 6 cards.


Surprise StrikeIf this Pokémon was on the Bench and became an Active Pokémon this turn, this attack does 50 more damage.
If I move Yanmega from being an Active Pokemon to the Bench, and then back to Active again in the same turn, does it get the bonus damage?
Yes.