I wanted to know what were the difference between mdd with psychotic features and f20.9 schizophrenia unspecified. and what they are exactly?

Psychosis is delusions (fixed false beliefs), hallucinations (sensations that are not real, most commonly vision or hearing), or poor thought functions. In psychotic depression the primary problem is a depression so severe that psychosis manifests; in schizophrenia, psychotic symptoms are the essence of the syndrome as opposed to a degree of severity. I hope this helps.

Manic depressive disorder with psychotic features is a mood disorder while schizophrenia is a thought disorder. A computer psychological test can sensitively differentiate either comparing one against millions in data bases with 97% reliability valididty.