The history of this incarnation of Loki most likely mirrors that of his Earth-616 counterpart.
Being half-Frost Giant and only the adopted son of Odin, Loki always felt he was second to his adoptive brother Thor. Loki was also known for being a trickster. At some point probably not too long before meeting the heroes known as Power Pack, Loki tricked Thor into accepting a match to see if Thor could throw his hammer, Mjolnir, further than Loki could throw a stone. Thor accepted and won, but threw his hammer so far it did not come back to him, just like Loki intended. After a long search, Thor was able to reclaim his hammer from Hrymer, which earned him the hatred of the Giant King.
Loki eventually hatched a plan along with Amora the Enchantress and Hrymer that would allow them to steal the Golden Apples of Idunn which grant the Asgardians their eternal youth. For the plan to succeed however, they needed to smuggle four magical gems into the walls of Asgard, which would allow Enchantress to cast a de-aging spell on the Asgardians. Loki first tried to trick the Avengers, X-Men, the Fantastic Four and even the Skrull Kill Krew into carrying out his plan, but they didn't fall for it. Eventually, he settled for Power Pack.
Knowing that their grandmother was dying from an illness, Loki visited the four kids under the guise of a nurse named Hloeja, and gave Julie a book about Norse mythology. Just like Loki hoped, Julie read about the apples and convinced her siblings to try and get these to cure their grandmother. To provide the kids easy access to Asgard, Loki send a pack of Wargs to attack the Pet Avengers. Power Pack subdued the Wargs and used them as steeds to reach Asgard. Once they arrived there, Loki disguised himself as an old merchant named Koil and pretended that he too was looking for the apples to help his sick wife. He provided Power Pack with Asgardian clothes so they could blend in with the Asgardians. These clothes however contained the gems. When Power Pack met up with Thor and Beta Ray Bill, Loki had Hrymer attack them. Just like planned, Power Pack helped Thor defeat the giant and in return was allowed to come with him to Odin to ask for the Golden Apples. This way, Power Pack unknowingly brought the gems within Asgards walls, and Enchantress was able to use her spell, turning all Asgardians into babies.
With this stage of his plan completed, Loki, once more under the guise of Koil, tricked Power Pack into getting the Golden Apples for him, claiming that Idunn could no longer do so now that she too was a baby. Power Pack, minus Alex, fell for it and brought the apples back to Loki, who then revealed his true identity and plan. He had Enchantress capture the heroes and summoned his Frost Giant army to attack the now defenseless Asgard while the Asgardians began to rapidly age now that they no longer had the Golden Apples.
However, at this point it turned out Loki's plan did contain one big flaw; the rapid aging of the Asgardians started Ragnarok and awoke the giant serpent Jormungand. His arrival in Asgard drove off Loki's army. Power Pack, Thor and even the Pet Avengers tried to fight the beast off, with no success, until Alex grabbed Mjolnir and was granted Thor's powers. At Julie's request, Thor destroyed the gems, which caused Enchantress' spell to backfire against her, Loki and Hrymer. All three were turned into babies, after which Julie easily tricked baby-Loki into giving her the apples, ending Ragnarok.
Loki was still a baby when Thor returned Power Pack to Earth.