The geometries of the ammonia complexes of $Ni^{2+}$,$Pt^{2+}$ and $Zn^{2+}$,respectively,are

How many unpaired electrons are present in $Ni^{2+}$?

Which of the following is not a square planar complex?

Consider the following test for a group-$IV$ cation.
$M^{2+} + H_2S \rightarrow A$ (Black precipitate) $+$ byproduct
$A + \text{aqua regia} \rightarrow B + NOCl + S + H_2O$
$B + KNO_2 + CH_3COOH \rightarrow C + \text{byproduct}$
The spin only magnetic moment value of the metal complex $C$ is $BM$. (Nearest integer)

Predict the number of unpaired electrons in the square planar $[Pt(CN)_{4}]^{2-}$ ion.

Which of the following configurations will show an outer orbital octahedral complex?