It is paramagnetic.
It absorbs light at a longer wavelength as compared to [Co(en)(NH3)4]3+.
It will have three geometrical isomers if bidentate 'en' is replaced by two cyanide ligands.
It has two geometrical isomers.
(A) [Co(en)(NH3)3(H2O)]+3 complex is type of [M(AA)b3c] which will have two geometrical isomers (B) If (en) is replaced by two cyanide ligands, the complex will be type of [Ma3b2c] and have 3 geometrical isomers (C) [Co(en)(NH3)3(H2O)]3+ have d6 configuration (t2g6) on central metal with strong field ligands, therefore it is diamagnetic in nature (D) Complex [Co(en)(NH3)3(H2O)]3+ have lesser CFSE (Δo) value than [Co(en)(NH3)4]3+ therefore complex [Co(en)(NH3)3(H2O)]+ absorbs longer wavelength for d-d transition.