In an octahedral complex of the type $Ma_3b_3$,where $M$ is a metal ion and $a$ and $b$ are two different types of ligands,what are the two possible geometric isomers?

Which one has the highest paramagnetism?

Number of possible isomers for $[Cr(H_2O)_2(C_2O_4)_2]^{-}$ are . . . . . . .

Complex $X$ of composition $Cr(H_{2}O)_{6}Cl_{n}$ has a spin-only magnetic moment of $3.83 \ BM$. It reacts with $AgNO_{3}$ and shows geometrical isomerism. The $IUPAC$ nomenclature of $X$ is

The pair$(s)$ of coordination complexes/ions exhibiting the same kind of isomerism is(are)
$(A)$ $[Cr(NH_3)_5Cl]Cl_2$ and $[Cr(NH_3)_4Cl_2]Cl$
$(B)$ $[Co(NH_3)_4Cl_2]^+$ and $[Pt(NH_3)_2(H_2O)Cl]^+$
$(C)$ $[CoBr_2Cl_2]^{2-}$ and $[PtBr_2Cl_2]^{2-}$
$(D)$ $[Pt(NH_3)_3(NO_3)]Cl$ and $[Pt(NH_3)_3Cl]Br$

The total number of possible isomers for the complex compound $[Cu^{II}(NH_3)_4][Pt^{II}Cl_4]$ are