What is the geometry of the $[Ni(CO)_4]$ complex?

The number of isoelectronic species among $Sc^{3+}$, $Cr^{2+}$, $Mn^{3+}$, $Co^{3+}$, and $Fe^{3+}$ is $n$. If $n$ moles of $AgCl$ are formed during the reaction of the complex with the formula $CoCl_{3}(en)_{2}NH_{3}$ with excess $AgNO_{3}$, then the number of electrons present in the $t_{2g}$ orbital of the complex is . . . . . . .

Identify the $CORRECT$ set of details from the following:
$A$. $[Co(NH_{3})_{6}]^{3+}$: Inner orbital complex; $d^{2}sp^{3}$ hybridized
$B$. $[MnCl_{6}]^{3-}$: Outer orbital complex; $sp^{3}d^{2}$ hybridized
$C$. $[CoF_{6}]^{3-}$: Outer orbital complex; $d^{2}sp^{3}$ hybridized
$D$. $[FeF_{6}]^{3-}$: Outer orbital complex; $sp^{3}d^{2}$ hybridized
$E$. $[Ni(CN)_{4}]^{2-}$: Inner orbital complex; $sp^{3}$ hybridized
Choose the correct answer from the options given below:

$d^{2}sp^{3}$ hybridisation of the atomic orbitals gives

Identify the number of unpaired electrons present and the geometry of the $[Co(NH_3)_6]^{3+}$ complex,respectively.

Which of the following compounds is diamagnetic and tetrahedral?