Which coordination number is associated with geometric isomerism in coordination compounds?

In which of the following compounds does the central metal atom have the maximum number of unpaired $e^-$?

Atomic numbers of $Cr$,$Fe$,and $Co$ are $24$,$26$,and $27$ respectively. Which of the following inner orbital octahedral complexes are paramagnetic?

Coordination isomerism is formed by the interchange of ligands between which of the following?

Consider the following complex compounds and identify the compounds which are optically active.
$I.$ $[Co(NO_2)_3(NH_3)_3]$
$II.$ $cis-[RhCl_2(NH_3)_4]^+$
$III.$ $[Cr(OX)_3]^{3-}$
$IV.$ $cis-[PtCl_2(en)]$
$V.$ $trans-[Cr(en)_2Br_2]^+$
$VI.$ $cis-[Cr(en)_2Br_2]^+$

Given below are two statements,one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A:$ The spin only magnetic moment value for $[Fe(CN)_6]^{3-}$ is $1.74 \ BM$,whereas for $[Fe(H_2O)_6]^{3+}$ is $5.92 \ BM$.
Reason $R:$ In both complexes,$Fe$ is present in $+3$ oxidation state.
In the light of the above statements,choose the correct answer from the options given below: