This Gym battle is hard it has one Rare Candy to defend aginst two gym leaders Chuck and jasmine.In the hacked version you get three rare candy to defend . If you win, you'll get the TMs Iron Tail and Focus Punch. The badges you will get is the Mineral badge and the Storm badge.
You can see ho-oh at the entrance of Olivine city. If you talk to it it will show you the cut-scene that you see when you talk to it upon entering the city.