Diamond 2 and Pearl 2.
20 years after DP.
November 2021.
Male rival, named Dusk. He is the son of Lucas and Dawn.
Your character is the grandson of Rowan. Rowan is much older now and retired.
Cyrus plays a HUGE role in the story. He is now a Pokemon doctor.
Evil team is Team Revived Galactic. Same commanders but they are much older. Leader is Comet, and he is Cyrus' son. Cyrus talks about how back during the events of DP, he had a child (mother passed away). Comet's goal is to revive Dialga/Palkia and finish what Cyrus tried to do back in DP.
As DP took place in Winter, these games are in Fall. . There are many trees with orange leaves and orange leaves are scattered in different places on the ground on many routes. Twice a month (on random days) there is a festival in Hearthome, with many things to do.
The contests, underground, and battle frontier return.
Pokemon follow you
You can move the camera everywhere, but there is only one wild area. The wild area is Mount Coronet.
The towns and routes are much larger and have changed a bit. Sinnoh is much larger and more immersive.
The largest building in the game is Sinnoh University, and it's a college in Canalve City. The main characters father is a teacher there.
Cynthia is an assistant to Looker.
Champion is Dawn if you play as the boy, and Lucas if you play as the girl. Their ace is the other box legendary.
No regional forms, instead, many Sinnoh Pokemon get future forms, including all the legendaries. All future forms keep their primary type, and get a new one. I saw: Torterra (Grass/Ice), Infernape (Fire/Dark), Empoleon(Water/Ghost), the Shinx line (Electric/Ice), the Starly line (Flying/Ground), the Buizel line (Water/Fighting), the Gible line (Dragon/Steel), Dialga(Dragon/Grass), and Palkia (Dragon/Fairy).
Future forms is the gimmick for this game, there is no dmax or megas.
All new story, it is longer than the originals.
No hms.
4 new gym leaders.
New prof, his name is Prof. Eucalyptus.