Is it true that all goddesses (e.g. Ambe, Vaishnodevi and other goddesses) are actually body parts of Sati Devi?
From Sati's Wikipedia page-
Daksha once organized a grand yajna to which all the gods were invited, with the exception of Sati and Shiva.
Sati goes there uninvited without Shiva. Sati was received coldly by her father. Every passing moment made it clearer to Sati that her father was entirely incapable of appreciating the many excellent qualities of her husband. The realization then came to Sati that this abuse was being heaped on Shiva only because he had wed her; she was the cause of this dishonor to her husband. She was consumed by rage against her father and loathing for his mentality. Calling up a prayer that she may, in a future birth, be born the daughter of a father whom she could respect, Sati invoked her yogic powers or yogic Agni which was attained by her due to severe devotion or puja done by her and immolated herself.
According to some traditions, it is believed that an angry Shiva performed the fearsome and awe-inspiring Tandava dance with Sati's charred body on his shoulders. During this dance, Sati's body came apart and the pieces fell at different places on earth.
According to another version, Shiva placed Sati's body on his shoulder and ran about the world, crazed with grief. The Gods called upon the god Vishnu to restore Shiva to normalcy and calm. Vishnu used his Sudarshana Chakra to dismember Sati's lifeless body, following which Shiva regained his equanimity.
Both versions state that Sati's body was thus dismembered into 51 pieces which fell on earth at various places. Several different listings of these 51 holy places, known as Shakti Peethas, are available; some of these places have become major centers of pilgrimage as they are held by the Goddess-oriented Shakta sect to be particularly holy. Besides 51 main Shakti pethas, some small peethas like Bindudham have also in existence which are due to Sati's fallen blood drops.
But three Pindi's of Veshno Devis is out of this 51 Shakti Peethas. Even there is contradictions in this counts in all stories.
From Vaishno Devi Wikipedia page
Vaishno devi is one of 108 shakti peetha, the story of Vaishno Devi is found in Chandi uppurana. When Vishnu Bhagwan cuts Sati Maa's body into 108 peethas then 52 body parts fell onto earth atmosphere and rest of the 56 fell on other planets. Out of which the "Blessing Hand" of Goddess Sati had fallen on "Planet Venus" or Shukra.
From the same Veshno devi page its is told that Three Pindi's are Made by three Goddess ( Shakti, Sarasvati and lakshmi). So other goddess are not made by part of Sati's body but this Shakti peetha's are. And the girl Kumari made of Parvati's physical appearance, soul of "Lakshmi" and Goddess of knowledge, Saraswati. Which is know as Veshno Devi in Bhairav Katha.
1did the sati practice originate from here ? Apr 22, 2017 at 6:49
No. All are not body parts of Devi Sati. It is only the Satipeethas that are known to have Sati's body parts. The number and locations also vary from one tantra to another, the range being four (in Ppranatoshini Tanta) to 51(Peethanirnaya Tantra).The body parts mentioned also vary in different scriptures.
Also, there are Upapeethas that contain the ornaments or clothes etc of Devi Sati.
And there are siddha peethas.
In India, there are hundreds of Devi temples.Among them maximumm Satipeetha containing the body parts are at best 51. (Ref:Shastramulak Bharatiya Shaktisadhana, Upendrakumar Das, vol 1, chapter 6.