Like Ramayan and Mahabharat, Is there any epic happened or yet to happen in Kaliyuga?
Duplicate of Which epic happens in Kali yuga, like Ramayana happened in Treta yuga and Mahabharata happened in Dwapara yuga?
It is said that all the four Yugas have repeated multiple times. And every Yugas events were written in puranas but except of Kali Yug, why?
Wrong question, events of Kali Yuga are written in Pratisarga Parva of Bhavishya Purana and in 6th part of Vishnu Purana.
If you can read Hindi then, you may read this (Introduction page 6 - 16 and Pratisarga Parva from page 234 - 275). Or in summary, you can read from this (page 843 to 855) or this.
From this question do Vedas talk about Avatars? The answer says yes then what about Kalki Avatar written in Veda?
Vedas talk about only few Avataras and not all. Puranas tell about all avataras.