How many geometrical isomers are possible for the complex $[Ma_3b_3]^{\pm n}$?

Which of the following complexes exhibits optical isomerism?

Which of the following compounds will exhibit coordination isomerism?

For an octahedral complex $MX_{4}Y_{2}$ ($M=$ a transition metal,$X$ and $Y$ are monodentate achiral ligands),the correct statement among the following is

Identify a $CORRECT$ formula for spin only magnetic moment.

Identify the complex which exhibits optical isomerism.