Niantic has launched the Throwback Challenge 2020: Kanto in Pokémon GO. This Kanto-themed challenge is now underway and is running for 10 days, asking players of the immensely-popular mobile game to fulfill research tasks that revolve around Kanto Pokémon. Be sure to check it out for yourself to see all the tasks you can now take on!
Trainers, research was released to some Trainers ahead of schedule. The event details will be released in the near future, meanwhile Trainers who received this research can complete it now but won’t receive it again. Sorry for the confusion!
Source: Official Pokémon GO blog