With reference to aqua regia, choose the correct options(s)

Aquaregia is a mixture of conc.HCl and conc.${\mathrm{HNO}}_3$ in 3:1 ratio. 

When gold dissolves in aquaregia, the species formed is ${\mathrm{AuCl}}_4^{-}$ in which gold is in +3 oxidation state. 

$\mathrm{Au}+{\mathrm{HNO}}_3+4\mathrm{HCl}\to {\mathrm{H}}^{+}+{\left[{\mathrm{AuCl}}_4\right]}^{-}+2{\mathrm{H}}_2\mathrm{O}+\mathrm{NO}$

In the absence of air the reaction between gold and aquaregia ${\mathrm{NO}}_2$ will not be produced. Yellow colour is due to the presence of NOCl and ${\mathrm{Cl}}_2$.