I have read lots of references about lord varaha but I wanna know the actual truth. From where and whom did lord varaha came from? In which timeline? What happened after? Is he mentioned in Vedas?
One of the avatharas of Lord Vishnu is the Varaha Avatharam. This is the third avathar that Lord Vishnu took and the Varaha Avatharam was a wild boar. This story is in the puranas. I will give a brief explanation as of what I have read. In this birth of the ishnu Avathara, the two guards Jaya and Vijaya were born as Hiranyaksha and Hiranyakashipu, two demons. Hiranyaksha got a boon from Brahma that he will not be killed by any God, beast, human, Asura, Devtha, and animal. Hiranyaksha became evil and he started torturing people. Then he grabbed the earth and threw it into the ocean of the paathala loka. Then King Manu came to Brahma and asked for his help. But Brahma was the one who granted the boon. So they all turned to Lord Vishnu, who immediately to the form of varaha, the wild boar. So varaha slays the demon after thousands of years of fighting, and carried the bhoomi and puts it back in place. After the varaha avathar's job was done, Shiva killed it because Vishnu was not able to control it's anger and then Hiranyakashipu comes in the story of Lord Narashimha, who comes right after Varaha Avathar, due to his anger. This all happens in the Sathya Yuga.
These are my sources: One, two, three(do check the index for the third souce for 3.1.2: Birth of Brahma and Salvation of Earth by Varaha and also the 8th Purana (Varaha Purana), and the 10th Purnana (Agni Purana)).