Which of the following exhibits coordination isomerism?

Identify the ionization isomer of $[Cr(H_2O)_4Cl(NO_2)]Cl$.

The correct order of the number of unpaired electrons in the given complexes is
$A$. $[Fe(CN)_6]^{3-}$; $B$. $[FeF_6]^{3-}$; $C$. $[CoF_6]^{3-}$; $D$. $[Cr(oxalate)_3]^{3-}$; $E$. $[Ni(CO)_4]$
Choose the correct answer from the options given below:

Of the following,which is diamagnetic in nature?

The complex having the highest spin-only magnetic moment is

Amongst $Ni(CO)_4$,$[Ni(CN)_4]^{2-}$ and $[NiCl_4]^{2-}$,which of the following statements is correct regarding their magnetic properties?