Different lists of Vishnu's avatars appear in different texts, including: the dasavatara from the Garuda Purana; lists of twenty-two, twenty-three, and sixteen avatars in the Bhagavata Purana; thirty-nine avatars in the Ahirbudhnya saṃhitā; the dasavatara again in Agni Purana; the first eight of the dasavatara in Padma Purana.

Vishnu Dharmottar Purana

The story of Dhruva is an ancient Indian myth found in Hindu texts such as the Vishnu Purana and the Bhagavata Purana. It is attributed to the sage Narada, who is said to have narrated the tale to Dhruva himself.

There is a book of prophesy not not many believe in it. It is Bhavishya Purana. Basically people interpolate what has already happened. Bhavishya Purana professes even the reign of Queen Victoria. The only prophecy that hindus believe is that the tenth avatara of Vishnu would come 427,000 years from now.

There are many Puranas and there are even new ones being created to this day. However, there are about 19 main ones about to the main Hindu deities like Agni, Vayu, Vishnu, Shiva and Brahma. The Bhagavad Purana is about Krishna. There are also Puranas about Vishnu's avatars (like the Matsya Purana).