What is the final chemical form of Gold $(Au)$ when it is dissolved in aqua-regia?

Give reason to explain why $ClF_3$ exists but $FCl_3$ does not exist.

An oxide of chlorine with water gives the strongest acid. The ratio of chlorine and oxygen in its formula is

$A$ solid $A$ which has photographic effect reacts with the solution of a sodium salt $B$ to give a pale yellow precipitate $C$. The sodium salt $B$ on heating with concentrated $H_2SO_4$ gives brown vapours. Identify $A$,$B$,and $C$.

Which of the following properties increases on going down from $F$ to $I$ in Group $17$ of the periodic table?

The correct statement$(s)$ regarding $(i) HClO$,$(ii) HClO_2$,$(iii) HClO_3$,and $(iv) HClO_4$ is(are):
$(A)$ The number of $Cl=O$ bonds in $(ii)$ and $(iii)$ together is two.
$(B)$ The number of lone pairs of electrons on $Cl$ in $(ii)$ and $(iii)$ together is three.
$(C)$ The hybridization of $Cl$ in $(iv)$ is $sp^3$.
$(D)$ Amongst $(i)$ to $(iv)$,the strongest acid is $(i)$.