Which of the following does not have optical isomers?

For the octahedral complexes of $Fe^{3+}$ in $SCN^{-}$ (thiocyanato-$S$) and in $CN^{-}$ ligand environments,the difference between the spin-only magnetic moments in Bohr magnetons (when approximated to the nearest integer) is
[Atomic number of $Fe = 26$]

Determine the magnetic property of $[CoF_6]^{3-}$.

The existence of two different coloured complexes with the composition of $[Co(NH_3)_4Cl_2]^+$ is due to

Given below are two statements:
Statement $I$: $A$ solution of $[Ni(H_2O)_6]^{2+}$ is green in colour.
Statement $II$: $A$ solution of $[Ni(CN)_4]^{2-}$ is colourless.
In the light of the above statements,choose the most appropriate answer from the options given below:

The coordination number,oxidation number,number of electrons in $d$-orbital,and number of unpaired electrons respectively in the complex $[Co(NH_3)_4CO_3]ClO_4$ are . . . . . . .