Which pair of the following complexes has the same $EAN$ for the metal atom/ion?

Which of the following follows the $EAN$ rule?

Select the odd one w.r.t. $EAN$ :-

Among $V(CO)_6$,$Cr(CO)_5$,$Cu(CO)_3$,$Mn(CO)_5$,$Fe(CO)_5$,$[Co(CO)_3]^{3-}$,$[Cr(CO)_4]^{4-}$,and $Ir(CO)_3$,the total number of species isoelectronic with $Ni(CO)_4$ is. . . . . [Given atomic number : $V=23$,$Cr=24$,$Mn=25$,$Fe=26$,$Co=27$,$Ni=28$,$Cu=29$,$Ir=77$ ]

In the complex $Fe(CO)_x$,the value of $x$ is :

Calculate the $EAN$ (Effective Atomic Number) of platinum in potassium hexachloroplatinate $(IV)$.