https://www.gamespot.com/articles/last-chance-to-get-these-free-legendaries-in-pokem/1100-6456999/

The end of the month is quickly approaching, which means 3DS players only have a little time left to claim the first of this year's many free Pokemon in Pokemon Ultra Sun and Ultra Moon. Players have until February 28 to pick up a free download code from GameStop, which will net you one of the cover monsters from Diamond and Pearl, Dialga and Palkia.

The download code can be redeemed in any seventh generation Pokemon title, and the Legendary you'll get depends on which version you're playing. Those with a copy of Ultra Sun or Sun will receive Palkia, while Ultra Moon and Moon players will get Dialga. Each Pokemon also comes at a different level and knows a slightly different moveset depending on your version. You can see what moves they'll know in each game at the bottom of this story.