1) This variation does not exist in the Vyasa Bagavan’s Mahabharata. Yamadharma came there only to test Yudhistra for his Knowledge and Wisdom. There is no Kaalaka Muni episode.
2) Villi Bharatham:
(i) This following variation is from 'Villi Bharatham' (வில்லி பாரதம்) a Tamil poetic translation of Mahabharata by Villiputhur Alwar (வில்லிபுத்தூர் ஆழ்வார்).
Duriyodana, Duchatana, Sakuni and Karna requested one sage Kaalaka Muni to perform a yagna to kill Pandavas. A demon came out at the end of the evil yagna. The demon was ordered to kill Pandavas. The demon told Kaalaka Muni that he can kill by eating Pandavas alive. The Demon added that if he could not find Pandavas alive on that day he would come back and eat the Kaalaka muni.
Yamadharma after knowing this wanted to save Pandavas. He made a big plan. He took a form of deer and took away the deer-skin of a Brahmin in the forest. The Brahmin sought the help of Pandavas. The Pandavas ran after the deer. The deer vanished afterwards. Yamadharma made the poisoned-water pond and all the four younger Pandavas died after taking water, not obeying the words of Yakshan (Yamadharma).
When Yudhistra was about to come near the pond he lost his consciousness due to excess heat and fell like dead. The Demon came then and recognized Yudhistra, the eldest of Pandavas. Thinking him as not alive, the demon walked to the pond and saw the other dead four Pandavas. The demon understood the reason correctly that they died of drinking the poisoned- water of the pond. The demon thought that his aim was to eat Pandavas alive but they were already dead. He returned back and ate Kaalaka Muni alive.
Yamadharma got back his consciousness because he fell under a sandalwood tree due the over heat subsidized. Then he answered all the questions (around 123 questions) and all the four came alive. The Yamadharma informed them the evil mind of Duriyodana & other three, the evil yagna, the demon, the end of Kaalaka Muni and on the vanished deer.
3) Here in Villi Bharatam, Yamadharma did not ask Yudhistra to sleep behind the dead body of Sahadeva. Probably it may be a third version and it is also a clever plan!
4) Reference, Books, Personal Collection:
(i) Villi Bharatham, (Original Tamil Poetic Version), Arumuga Navalar edition, Vidyanupalana Yantra Sala, Chennai, Eleventh Edition, Year Publication, 1922, Pages 177 to 184 (நச்சுப்பொய்கைச்சருக்கம், poison-pond chapter), Total pages 416
(ii) ‘Villi Bharatha Vachanam (Tamil Prose order Villi Bharatham), M V Govindaraja Iyengar, Vasan Bookstore, Ananda Vikatan press, Year Publication, 1929, Pages 304 to 316, Total Pages 736.