Which of the following complexes exhibits a square planar geometry?

In solid $CuSO_4 \cdot 5H_2O$,copper is coordinated to:

The $d$-electronic configuration of $[CoCl_4]^{2-}$ in a tetrahedral crystal field is $e^m t_2^n$. The sum of '$m$' and the number of unpaired electrons is $.............$.

The shape of $MnO_4^-$ ion and the hybridisation of $Mn$ in $MnO_4^-$ is

The spin-only magnetic moment of $[MnBr_4]^{2-}$ is $5.9 \ BM$. Predict the geometry of the complex ion.

For which of the following $d^n$ configurations of octahedral complexes,can they $NOT$ exist in both high spin and low spin forms?
$(I)$ $d^3$,$(II)$ $d^5$,$(III)$ $d^6$,$(IV)$ $d^8$