Which one of the following is the true covalent oxide of iodine?

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 $Cl_2$.

Among the following,which is the strongest oxidising agent?

How can you prepare $Cl_2$ from $HCl$ and $HCl$ from $Cl_2$? Write reactions only.

Identify the incorrect statement among the following.

Which of the following is prepared by the electrolytic method?