you cant
No.
no you cant
Without trading, cheating, or Nintendo events, you can get Dialga, Uxie, Azelf, Mesprit, Heatran, Giratina, and Cresselia.
you can't get mewtwo only by trading or Nintendo events
its imposibble without trading.
Unfortunately you can't. The only way to get it in "Sapphire" is by trading or by a cheating device. The events for that generation are over - likely for good.
Nope.
you can trade or find him and catch it how you mostly do
146
Nintendo event.
go to the next Nintendo event.
You can't catch Shaymin without cheats or a Nintendo event.