Hoe to get shaymin

Answer 1

you need an Action Replay.

insert it and select the game youre playing.

choose "One of every item" (or something along those lines)

then you will have the letter from Professor Oak.

if you go to the flowery place with the shiny rock that you can see yourself in, run until you see Oak. Talk to him.

After you talk to him (either in front of you or you have to walk) Shaymin will appear.

(im not sure if this is all correct i checked serebii.net and this is what i was told and i remember.)