Indicate the types of isomerism exhibited by the following complexes and draw the structures for these isomers:
$(i)$ $K[Cr(H_2O)_2(C_2O_4)_2]$
$(ii)$ $[Co(en)_3]Cl_3$
$(iii)$ $[Co(NH_3)_5(NO_2)](NO_3)_2$
$(iv)$ $[Pt(NH_3)(H_2O)Cl_2]$

(N/A) $(i)$ $K[Cr(H_2O)_2(C_2O_4)_2]$ exhibits geometrical isomerism (cis and trans forms) and optical isomerism (the cis-isomer is optically active).
$(ii)$ $[Co(en)_3]Cl_3$ exhibits optical isomerism due to the presence of the bidentate ligand $en$ (ethylenediamine),forming non-superimposable mirror images (d and l forms).
$(iii)$ $[Co(NH_3)_5(NO_2)](NO_3)_2$ exhibits linkage isomerism because the $NO_2^-$ ligand can coordinate through either the $N$ atom or the $O$ atom $(ONO^-)$,and ionization isomerism due to the exchange of $NO_2^-$ and $NO_3^-$ ions.
$(iv)$ $[Pt(NH_3)(H_2O)Cl_2]$ exhibits geometrical isomerism (cis and trans forms) due to the square planar geometry of the $Pt(II)$ complex.