When Vishnu appeared before Vasudeva and Devaki in their prison cell in order to incarnate as Krishna, he told them about how he was born to them in previous births as well, as described in the Srimad Bhagavatam:
My dear mother, best of the chaste, in your previous birth, in the Svāyambhuva millennium, you were known as Pṛśni, and Vasudeva, who was the most pious Prajāpati, was named Sutapā. When both of you were ordered by Lord Brahmā to create progeny, you first underwent severe austerities by controlling your senses.... Since I am the best of all bestowers of benediction, I appeared in this same form... to ask you to take from Me the benediction you desired. You then expressed your desire to have a son exactly like Me....
Since I found no one else as highly elevated as you in simplicity and other qualities of good character, I appeared in this world as Pṛśnigarbha, or one who is celebrated as having taken birth from Pṛśni. In the next millennium, I again appeared from the two of you, who appeared as My mother, Aditi, and My father, Kaśyapa. I was known as Upendra, and because of being a dwarf, I was also known as Vāmana. O supremely chaste mother, I, the same personality, have now appeared of you both as your son for the third time.
My question is, what is the story of Vishnu's incarnation (avatara) Prishnigarbha? What was the purpose of this incarnation, and what did he do? I can't find much information on him. Prahupada claims in one of his purports that Prishnigarbha was the incarnation of Vishnu who appeared before Dhruva:
According to Śrīla Rūpa Gosvāmī in his Laghu-bhāgavatāmṛta, the Sahasraśīrṣā Personality of Godhead who appeared at that time was the incarnation known as Pṛśnigarbha.
But does this claim have any scriptural basis?
Also, Wikipedia says "King Suthapas and his wife ... gave birth to Prasnigarbhan who gave to the world the practice of Brahmacharya Vratha (Celibacy)." But it doesn't provide any sources. Are there any scriptures that mention this?
What other details about Prishnigarbha's life are mentioned in Hindu scripture?