Late Maariv on Motzaey Shabbas

If I missed Maariv Motzaey Shabbas and I say it at aroun 12:05 or any time much later do I still need to say Ata Chunantonu and everything which were supposed to say Motza Shabbas?

Shalom, Thank you for your question. Even though one should say then evening service at the beginning of the evening, and certainly before the middle of the night – one is still obligated to pray ma'ariv until dawn. Even when one is reciting ma'ariv after they have already said (or heard) havdallah one still recites the havdallah in the amidah (atah chonatanu) (see Mishna Brurah 294,1) . Also the other prayers we say on motzai Shabbat should be recited even when saying ma'ariv very late at night. Blessings.