Oxygen does not react with

In chromyl chloride test,the oxidation state of $Cr$ changes from

What are $X$ and $Y$ in the given reactions?
$2X_{2(g)} + 2H_2O_{(l)} \to 4H^{+}_{(aq)} + 4X^{-}_{(aq)} + O_{2(g)}$
$Y_{2(g)} + H_2O_{(l)} \to HY_{(aq)} + HOY_{(aq)}$

Bromine is obtained on a commercial scale from

Which of the following are correct matches?
$(a)$ $ClO_4^- > ClO_3^- > ClO_2^- > ClO^-$ (Stability order)
$(b)$ $Cl_2 > Br_2 > F_2 > I_2$ (Bond energy)
$(c)$ $OF_2 < OH_2 < OCl_2$ (Bond angle)
$(d)$ $I^- > Br^- > Cl^-$ (Reducing power)

$I_2$ dissolves in $KI$ solution due to the formation of