You get your 3rd badge in Veilstone city against Maylene.
you go the the fourth gym in pastora and battle him
hearthome i think
you cant
in eterna city
The mine badge.
== == You get the 8th gym badge in Sunyshore City. Hope this helps
Beat the gym leader
sunyshore
Veilstone City
Snowpoint City.
The third badge is in Goldenrod City.