Hi I’ve been wondering for a while if they update loot box rewards to incorporate shop skins from the previous season. For example, is it possible to get “Heart of Passion” kiriko from last season in a loot box? Also, I know that the ultimate battle pass skins (For example, “Heart of Courage” Freja and “Demon Rocker” Illari) are labeled shop skins, but since they are associated with the actual battle pass, are they not obtainable through lootboxes? I’m just curious as to how this whole rewards system is updated from season to season. Thanks 
You can see a full list of cosmetics that are available in the boxes on the lootbox page of the game. Just press the ability info button (f1 on pc) and start reading the long list of poorly edited cosmetic names.