Which type of isomerism is exhibited by $[Cr(C_2O_4)_3]^{3-}$?

Which of the following is not correctly matched?

How many isomers are possible for the complex $[Co(en)_2Cl_2]^+$?

Which of the following compounds is colored but does not contain any unpaired electrons?

Which of the following complexes will exhibit the highest number of isomers?

Among the following complexes $(K-P)$,
$K_3[Fe(CN)_6]$ $(K)$,$[Co(NH_3)_6]Cl_3$ $(L)$,$Na_3[Co(ox)_3]$ $(M)$,$[Ni(H_2O)_6]Cl_2$ $(N)$,$K_2[Pt(CN)_4]$ $(O)$ and $[Zn(H_2O)_6](NO_3)_2$ $(P)$,the diamagnetic complexes are