Which product is formed when fluorine reacts with hot and concentrated sodium hydroxide?

Which of the following is the most active halogen?

$HBr$ and $HI$ can reduce sulfuric acid; $HCl$ can reduce $KMnO_4$. Which of the following can $HF$ reduce?

$X_2$ reacts with water to form $HX_{(aq)}$ and $HOX_{(aq)}$. $Y_2$ reacts with water to form $O_{2(g)}$,$Y^{-}_{(aq)}$ and $H^{+}_{(aq)}$. $Z_2$ does not react with water. $X_2, Y_2, Z_2$ are respectively

Which one of the following statements is not correct?

The number of halogen$(s)$ forming halic $(V)$ acid is ..... .