There are 16 badges in total, 8 from Johto and 8 from Kanto.
They are:
you have to get all the gym badges in kanto
the first seven badges are with the gym leaders that you have to defeat
every single one except his
In Cerealean cave after you get all the kanto gym badges
you get it after you have all the gym badges from kanto and johto regions.
You get it from professor oak after you obtain all 16 gym badges
u get it from blue once you get all eight gym badges in kanto
When u get all 8 kanto gym badges,I think;~]
You can get all sixteen badges by defeating all eight Johto gym leaders, defeating the Elite 4, and then beating all eight Kanto gym leaders.
we can get 8 gym badges byfighting all the gym leaders in Pokemon pearl.
you need all the 16 gym badges and then go through the cave
Delete EVERYTHING from your bag , then use cheat. [cannot work if you have all16 gym badges]