As I promised Lukie, I would cover Goldenrod. ♥
Goldenrod's become golden, at long last. There's not much change except for the addition of the
GTS [exact same layout as in Platinum], the movement of the Radio Tower location, and the addition of a fortune teller stand near the north gate.
So, let's get started!
Up in the front is the
department store. To the right is the bicycle store. A bike is free because the owner's poor location is costing him patronage, and so he decides if you ride one of his bikes, you'll advertise for him & that's worth losing a bike for in his eyes.
Go up further until you reach
the gym. You'll see someone of relation to the gym leader, Whitney, blocking the entrance. She'll say Whitney's gone out. Head over to the radio tower.
The radio tower is right next to the train station [something you don't need to worry about until you get to Kanto]. Go into the tower and talk to the lady to the left of the pink-haired girl [that's Whitney].
Answer 5 questions correctly and you'll get a radio app for your Pok�gear. Whitney will react and walk back to her gym if you succeed. Go back to the gym and beat Whitney. She'll run off crying, refusing to give you the badge. If memory serves, go into the house to the right and the lady occupying the building will convince Whitney to stfu. Don't forget to receive the Squirtbottle from her as well. You need it to progress after the Bug Catching Contest.
Now you should have some time to kill. Go underground through one of the buildings containing a depressing staircase.
Pick up the Coin Case concealed as a Pok�ball and go over to the
Game Corner for some fun.