its at the top part of slateport;go to the northernmost part of the city then take a right.

hope this helped

Ahead North of Mauville, you go to Mt. Chimmney

the potion is in the pharmacy in cianwood city

You must have the first 7 gym badges before you can continue ahead to Sunnyshore. Also I beat Cyrus and caught Giratina [platinum version].

You go to the dragon's den (you need surf for this) then you go up the gym and there will be a house up ahead and you have to fight the old guy in the back. After that the gym leader will come in and give you your badge.