Which of the following statements is $NOT$ correct regarding the complex $[Co(NH_3)_6]^{3+}$?

The magnetic moment of $[MnX_4]^{2-}$ is $5.9 \, BM$. The geometry of the complex ion is: ($X =$ monodentate halide ion)

$A$ complex with the composition $[MA_3B]^{n \pm}$ is found to have no geometrical isomers. The possible structure$(s)$ of the complex is/are (where $A$ and $B$ are monodentate ligands):

Which of the following statements are correct?
$i$. $[Mn(CN)_6]^{3-}, [MnCl_6]^{3-}$ both are paramagnetic
$ii$. Both $[NiCl_4]^{2-}, [Ni(CO)_4]$ are tetrahedral and diamagnetic
$iii$. $[Co(NH_3)_6]^{3+}$ is an inner orbital complex,but $[Ni(NH_3)_6]^{2+}$ is an outer orbital complex

The molecule in which hybrid $MOs$ involve only one $d-$orbital of the central atom is:

Which of the following complexes exhibits $sp^{3}d$ hybridization?