Go into the cave and use rock smash on the stone, you'ill get as reward hm 4 (strength) from that guy
you recieve the hm waterfall after you have deafeated the elite 4
HM 07 in emerald is waterfall
HM 05 is flash
Tropius and Gyarados together can learn all of the HM's.
No.
you cant our you will have to a cheat
strength after the chamber
talk to Wallace
H.M
HM02
Zigzagoon and liloone
the hiker in granite cave