Oxidation state of $Fe$ in $K_3[Fe(CN)_6]$

The $IUPAC$ name of $[Ni(NH_3)_4][NiCl_4]$ is

Which among the following is a correct formula of Pentammine aqua cobalt$(III)$ iodide?

As per $IUPAC$ norms,the name of the complex $[Co(en)_{2}(ONO)Cl]Cl$ is:

The $IUPAC$ name of ${K_2}[Cr(CN)_2(O_2)(O)_2(NH_3)]$ is

Write the $IUPAC$ names of the following coordination compounds:
$(a)$ $[Pt(NH_3)_2Cl(NO_2)]$
$(b)$ $K_3[Cr(C_2O_4)_3]$
$(c)$ $[CoCl_2(en)_2]Cl$
$(d)$ $[Co(NH_3)_5(CO_3)]Cl$
$(e)$ $Hg[Co(SCN)_4]$