Regirock, Regiice and Registeel. if you capture all three and transfer then to Pokemon Diamond/Pearl/Platinum you can go to the shrine in Snowpoint City to battle the master Regigiggas :)
you can't get the black flute in leaf green but you can in Pokemon ruby, sapphire and emerald then trade it to leaf green.
go to mossdeep city then head left and go past the white rock at the end their should be a house with a fisherman in it and he will give it to you
tm43 in emerald is secret power
latios and latias appear in random patches of grass and areas of water after you catch Rayquaza or make him faint.(after saving the world in Sootopolis.)
You can put plants in your secret bases in emerald
how to get all the tickets in Pokemon emerald?
SECRET
Loose trees, dents in rocks, and piles of grass are where you can build secret bases in Pokemon Emerald Version.
Unfortunately there is no TV in Ruby/Sapphire/Emerald for a secret base. Many people worldwide will be upset. :(
You cannot fight people in your secret base.
ABXY
Sadly, no. The creators of the game forgot to add in the Pokedex, so trading is impossible without GameShark. :(