During the tournament, all Pokémon are set to Lv. 50 during battle. Their stats are adjusted accordingly. All other aspects of the Pokémon remain the same, including moves known and Evolution.
For example, during a battle, a Lv. 100 Hydreigon that learned Outrage at Lv. 79 would be reduced to Lv. 50 and its stats would be adjusted to what they would be at Lv. 50. Though this would put Hydreigon below the level at which it evolved from Zweilous (as well as below the level at which it learned Outrage), it would remain a Hydreigon that knows Outrage. After the battle, Hydreigon would be returned to Lv. 100 and its stats would return to normal.
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