but actually like today we know abt God Kalki , the same way Treta yug ppl know abt Lord Ram, thats y they address him as GOD i mean prabhu. In valmiki Ramayan its written that sumant guided Dashrathji for putra kameshthi yagya as he rad in some puran abt dashrath will get son with this yagya. So Ramjis life was already written somewhere but RAMAYAN was first by Valmiki ji and he taught Ramayan to luv n kush. He even knew the end but didnt taught that part as kids will get disturb knowing abt mother sita.