strength after the chamber
RegiRock
you need to get to the sealed chamber look up sealed chamber to find out more
All
Only regirock, regice, registeel is available in Emerald
to get regirock in Pokemon platinum, you have to upload it from ruby, Sapphire, or emerald.
You can only get Regirock by transferring a Regirock from Pokemon Ruby, Saphire, or Emerald to the Pal Park I believe.
use the hm dive
In Diamond you can't catch Regirock, you have to migrate it from Pokemon Ruby, Sapphire, or Emerald.
You cannot get Regirock in Diamond without migrating one from Ruby, Sapphire or Emerald.
Go into the cave and use rock smash on the stone, you'ill get as reward hm 4 (strength) from that guy
HM 07 in emerald is waterfall
HM 05 is flash