What is the Effective Atomic Number $(EAN)$ of $Cu$ in $[Cu(NH_3)_4]^{2+}$?

If $E.A.N.$ of central metal cation $M^{2+}$ in a non-chelating complex is $36$ and atomic number of metal $M$ is $26$,then the number of monodentate ligands in this complex are

Choose the correct option regarding the following complex compounds which follow $(F)$ and do not follow $(NF)$ the Sidgwick $EAN$ rule:
$I. [(Ph_3P)_2PdCl_2PdCl_2]$
$II. [NiBrCl(en)]$
$III. Na_4[Fe(CN)_5NOS]$
$IV. Cr(CO)_3(NO)_2$
$I-II-III-IV$

The complex that violates the Sidgwick's rule of $EAN$ is

During the race of complex compounds,the finish line is fixed by achieving an $E.A.N.$ value equal to the atomic number of the corresponding inert gas. Which of the following complexes is present at the finish line?

Which of the following species can act as a reducing agent?