Optical isomers of $[Co(en{)}_3{]}^{3+}$

Answer the following questions.

Q$1$:

A$)$ Describe at least three basic methods for the resolution of optically active complexes$/$isomers$.$ Which one of these methods is used in the given experiment?

B$)$ Differentiate stereoisomers and enantiomers? Give at least three examples of each?

Q$2$: Explain Why?

a$.$ water is added to ethylenediamine solution and the mixture is kept on ice, prior to the addition of concentrated $HCl.$

b$.$ cobalt$($II$)$ sulphate solution is added to the mixture obtained in $($a$),$ followed by $1g$ of activated charcoal, followed by bubbling of air for $4h.$

c$.$ Barium $d(+)$ tartarate is added to the whole solution obtained after filtering off charcoal in $($b$).$

d$.$ Explain the difference between resolution of optical isomers and racemization?

$($Inorganic chemistry$)$