Kind of piggy-backing off of this old question, since it seems relevant. I hope that's all right!

Is it possible to obtain information in-character pertaining to the conditions of unlocking the fight against a gym leader's Elite team?

What about a list on past badge victors?

Yang is trying to find out if anyone has ever successfully cleared ALL badges and gone back for seconds with the elite teams, or similar information.

She was going to try to search out this info from libraries, newspapers, asking around at the Gyms, and also Pokemon Centers.