Solution

(i) Orbitals of $$ Co^{3+} $$ ion $$ d^2sp^3 $$ hybridised orbitals of $$ Co^{3+} [ Co(NH_3)_6]^{3+} $$ (inner orbital or low spin complex) .
No of unpaired electron $$ = 0 $$
Magnetic property = dimagnetic , due to absence of unpaired electrons
(ii) Electronic configuration is $$ 3d^6 $$ orbitals of $$ Fe^{2+} $$ ion :
As $$ CN^- $$ is strong field ligand, it causes the pairing of the unpaired $$ 3d $$ electrons. since there are six ligands around the central metal ion, the most feasible hybridization $$ d^2sp^3 ,d^2sp^3 $$ hybridized orbitals of $$ Fe^{2+} $$ are :
$$ 6 $$ electron pairs from$$ CN^- $$ ions occupy the six hybrid $$ d^2sp^3$$ orbitals. then
hence. the geometry of the complex and the complex is diamagnetic (as there are no unpaired electrons.)