IF you want to do it with one pokemon, Train either your starter or get a dustox/high-level Beautifly or Wingull. Otherwise, raise them evenly until they are about as strong as Roxanne's team (although they probably won't be exactly the same).
the third badge in sapphire is at mauville city(north of slateport city)
Go to lavaridge town for your next badge.
It is the balance badge where you fight Norman(your father) in Petalburg City .
Petalburg City.
You have to beat flannery
you can get the fith badge by going to petalburg the poke gym there.
In Pokekon Sapphire, you get the 5th badge after defeating your opponent in a Gym Battle at Petalburgh.
You get the third badge in sapphire when you get to Mauville. You have to battle Gym Leader Wattson in the Mauville City Gym.
Yes, the water stone from Pokemon looks like Sapphire.
in lavarage town
Have a ruby or another sapphire trade you a legendary!
the 4th badge. it also is the horse jumping through something with a ball in the middle