Which of the following is the strongest oxidizing agent?

The anhydride of perchloric acid $(HClO_4)$ is:

With reference to aqua regia,choose the correct option$(s)$.
$(1)$ Reaction of gold with aqua regia produces $NO_2$ in the absence of air.
$(2)$ Aqua regia is prepared by mixing conc. $HCl$ and conc. $HNO_3$ in $3:1$ $(v/v)$ ratio.
$(3)$ Reaction of gold with aqua regia produces an anion having $Au$ in $+3$ oxidation state.
$(4)$ The yellow colour of aqua regia is due to the presence of $NOCl$ and $Cl_2$.

Photographic films or plates have ......... as an essential ingredient.

Identify the incorrect statement about the interhalogen compounds.

Oxyacids of chlorine show similarity in