How many statement is/are correct for given complex  ${\left[Co{\left(C_2{O}_4\right)}_3\right]}^{3-}$
i) It contain negative charged ligands only
ii) The oxidation state of central metal atom is +3
iii) It is optically active
iv) Due to chelation the stability of the complex increases
v) It exhibit geometrical isomerism
vi) It is octahedral with $d^{2}s{p}^3$  hybridization.
Vii) If one oxalate ligand is replaced by glycinate ion then it form two enantiomeric pairs