A frozen Pokémon can still use the moves Flame Wheel, Sacred Fire, Flare Blitz, Fusion Flare, Scald, Steam Eruption, Burn Up, Pyro Ball, Scorching Sands, and Matcha Gotcha while frozen; these moves will thaw the user out, then execute normally. They will thaw out the user even if they are blocked, miss, deal no damage due an Ability like Flash Fire, or are prevented from being executed by Powder, heavy rain, or extremely harsh sunlight; however, they cannot thaw out the user if they would fail (such as a non-Fire-type Pokémon using Burn Up).
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I think this answers your question. Hopes this helps!
