Which of the following would exhibit coordination isomerism?

The difference in the number of unpaired electrons of a metal ion in its high-spin and low-spin octahedral complexes is $2$. The metal ion is

$[Fe(CN)_6]^{4-}$; $[Fe(CN)_6]^{3-}$; $[Ti(CN)_6]^{3-}$; $[Ni(CN)_4]^{2-}$; $[Co(CN)_6]^{3-}$
Among the given complexes,the number of paramagnetic complexes is .... .

Which of the following complexes exhibits the highest paramagnetic behaviour? (Where $gly = \text{glycine}$,$en = \text{ethylenediamine}$ and $bipy = \text{bipyridyl}$) (At. nos. $Ti = 22, V = 23, Cr = 24, Fe = 26, Co = 27$)

Which one has the highest paramagnetism?

The "spin only" magnetic moment of $Ni^{2+}$ in aqueous solution would be [At. no. of $Ni = 28$]