For the Mystery events thing do you need another gba and another pokemon..

For the mystery gift you need to have any of the gold silver or ruby sapphire games that do mysterygift and a regular gameboy. The screen should come up saying connect ir device and hit A or something like that. The ir stands for infra red device that's only found on the gameboy color. That's what the little red flat thing on the top is. Line up both of the gameboys and hit A. It should then say ??? sent ???, and the same for the other person. I do not know how to do the GBA because i don't have one anymore and never figured it out. You may have to look at the game book you got with the game to know where it is, or the instruction book that came with the GBA. If you have two rgular GBC then you can do gold and silver, but unless you know where the IR device is on the GBA then you can't do Ruby or Sapphire on the GBC, it won't fit.
I hope this at least gets you started.

The Mystery Events program for the Pokémon Ruby and Sapphire games does not serve the purpose that Mystery Gift did in Gold, Silver, and Crystal, so you won't have any luck with it linked between the two Ruby or Sapphire cartridges. This program can be used with the E-Reader to download new trainers to fight in Mossdeep City (watch the locked door...) or to acquire the Eon Ticket, or with the bonus disk that you received if you preordered Pokémon Colosseum to acquire Jirachi. It is also used to obtain Jirachi or Deoxys from the Nintendo tours. Mystery Gift, on the other hand, is used between Gold, Silver, and Crystal cartridges to spawn rare items and room decorations.

You'll need a E-Reader, a Link Cable, and, yes! another Game Boy Advance.

Also, when you Link up the E-Reader, you can swipe E-Cards.

Ya you need a mate for Mystery Event. You can get items such as Eon Ticket and Masterball. I suggest you get your freind for Mystery Event. You wont regret it.
VX-Filter ROCKS!!