During the tournament, all Pokémon are set to Level 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 Level 100 Hydreigon that learned Outrage at Level 79 would be reduced to Level 50, and its stats would be adjusted to what they would be at Level 50. Though this puts Hydreigon below the level at which it evolved from Zweilous, as well as below the level at which it learned Outrage, it remains a Hydreigon that knows Outrage. After the battle ends, Hydreigon is returned to Level 100, and its stats return to normal.
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