What is the Sinnoh Challenge?
If you collect them all, you will receive x3000 stardust, 15 ultra balls and a magnetic lure module. You will also get a badge and completing the challenge will count towards your Elite Collector Metal. The badge that you receive will have a number on it, showing what place you received before other trainers.
What are the new Pokemon?
You can also find the following Pokemon appearing in the world: Bidoof Drifloon Glameow, Purugly and Hippopotas.
How do I catch the Shadow Pokemon?
For Shadow Stunky, you will want to look for a Dark-type Team Rocket Grunt to battle against who is female and says “Where there is light, there is also a shadow”. That grunt will be the one that has the Stunky, but you might also get other Pokemon from her.
For Shadow Snover you will need to find an Ice-type Team Rocket Grunt, who will say “You’re gonna be frozen in your tracks.”
What about the other Pokemon?
Many of the others you will see in the world, but do continue hatching some eggs.