Question

Hydrogen support for combustion and oxygen also support for fire the then how H²O can remove fire

Answer 1

The properties of compound is different from it's constituents individual properties.
Here although hydrogen and oxygen, both support fire and are gaseous at room temperature. But H2O is used to extinguish normal fire, and H2O is liquid at room temperature as water.
So the properties differ once the elements/molecules form compounds.
Water is extinguisher as it removes heat from fire by cooling it down.

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