The complex that can exhibit linkage isomerism is

In $Cr^{2+}, Mn^{2+}, Fe^{2+},$ and $Ni^{2+}$,the number of electrons in the $3d$ orbital are $3d^4, 3d^5, 3d^6,$ and $3d^8$ respectively. Which of the following aqueous complexes will have the lowest magnetic moment?

The number of geometrical isomers for $[Co(NH_3)_3(NO_2)_3]$ is ....

The spin-only magnetic moment of an octahedral complex of $Fe^{2+}$ in the presence of a strong field ligand in $B.M.$ is $.....$

The number of possible isomers for the square planar complex $K_2[PdClBr_2SCN]$ is .................

Identify the incorrect match from the following: