If you mean while using an emulator, it depends on the emulator you are using.
Check in the options for the controls.
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its not an emerald its RAYQUAZA the main legendary Pokemon in Pokemon emerald.
Usually they don't mean anything, but for the GameShark you can use L and R for activating codes.
You cannot get a Yanma in Pokemon Emerald, as only Hoenn Region Pokemon can be found in Pokemon Emerald.
There is no Autosave in Pokemon Emerald.
defog is not in emerald,