in a diving spot
You have to migrate from Sapphire or Emrald.
cave of oragin
yes
go to the weather institute guy he will tell you were the weather in strange then go there so I hear
Groudon Kyogre Rayquaza Latias (u can only catch one, either latias or latios) Latios Regice Registeel Regirock
raquaza is at the sky pillar latias and latios will be found randomly kyogre is at the marine cave groudon is in the terra cave mew and deoxys are both at ilands
Nowhere.
You do not get
Yes
No.
in the sea
you get at navel rock