Which of the following complexes has a square planar geometry and $dsp^2$ hybridization?

The geometries of some complex ions are given below. Select the correct answer.
$(1) [Ag(NH_3)_2]^+ - \text{Linear}$
$(2) [MnCl_4]^{2-} - \text{Tetrahedral}$
$(3) [Cu(NH_3)_4]^{2+} - \text{Square planar}$
$(4) [Ni(CN)_4]^{2-} - \text{Square planar}$

Addition of excess aqueous ammonia to a pink coloured aqueous solution of $MCl_2 \cdot 6H_2O (X)$ and $NH_4Cl$ gives an octahedral complex $Y$ in the presence of air. In aqueous solution,complex $Y$ behaves as a $1:3$ electrolyte. The reaction of $X$ with excess $HCl$ at room temperature results in the formation of a blue coloured complex $Z$. The calculated spin-only magnetic moment of $X$ and $Z$ is $3.87 \ B.M.$,whereas it is zero for complex $Y$.
Among the following options,which statement$(s)$ is(are) correct?
$[A]$ The hybridization of the central metal ion in $Y$ is $d^2sp^3$
$[B]$ $Z$ is a tetrahedral complex
$[C]$ Addition of silver nitrate to $Y$ gives only two equivalents of silver chloride
$[D]$ When $X$ and $Z$ are in equilibrium at $0^{\circ}C$,the colour of the solution is pink

Assertion $:$ Complex ion $[Co(NH_3)_6]^{2+}$ is readily oxidized to $[Co(NH_3)_6]^{3+}$.
Reason $:$ Unpaired electron in complex ion $[Co(NH_3)_6]^{2+}$ is present in $4p$ orbital.

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

Identify the type of hybridization involved in the hexaamminecobalt$(III)$ complex ion.