Ramayan in other sacred texts

I am coming across references to the Ramayana in many other texts.
Srimad Bhagwad Purana has a reference to Rama and killing of Ravana. This book takes it further and talks about descendants of Rama.

Then there is Devi Bhagwad Purana. This Purana talks about Devi and her greatness. This Purana incidentally also has Ramayana here.This also talks about how Rama performed Navaratri and worshiped the Goddess.

This story of Rama praying to the Goddess does not find a mention in the Valmiki Ramayana, but is there Krittibasi Ramayan, the Bengali version of the epic.

This also gets to think about Ramayana. As this is mentioned in the various texts, was Ramayana something that had happened.

Also, who was Veda Vyasa, the author of Mahabharata and the Puranas? Was this a person  or a group of people, who knew the Vedas and had mastered them (A-Bhayas), thus getting a title Veda Vyasa?

No clue.

Its good to read and trying to understand and at the most, enjoy them.