Question

Can a didentate ligand act also as an ambidentate ligand ?

Answer 1

No because

A bidentate ligand is one which has two donor sites such that it can co-ordinate lone pairs from both the donor atoms simeltaneously to the metal atom/ion. Ex: ethylenediamine (en)

The ambidentate ligands have two donor sites but only one of the two atoms co-ordinate their lone pair at any given instant. Ex: in NO2–, the donor atom is nitrogen whereas in ONO-, the donor atom is oxygen.