Additionally, you can't use a GBA of any kind to trade or have other link functions between 2 GBC games. I've tried this myself (with both Pokemon and non-Pokemon games alike) and no, it doesn't work. To have any kind of link between 2 Pokemon games, you must use 2 of the system it was made for, and supply the appropriate Link Cable (exception: GBCs can sub for monochrome systems).
Just thought I should point that out, in case someone asks... - DNA

I traded between gold and silver on my GBASP and a GBA

Where can I find a lucky egg?

You can find them on wild Chanseys. Each wild Chansey has a 5% chance of holding a Lucky Egg. Which makes this item very rare indeed.

Quite untrue. Blinded has it right, you can trade between GSC on GBA and GBA SP.

The way to get your RSE Pokemon to DP is to "migrate" them. Although I'm not a proud owner of a DS and DP, so I can't tell you how to do this, sorry. As far as I know, however, you can't send them back to RSE.

What I've heard, is that the Everstone gives a 50% chance of passing on the female or Ditto's nature if the female/Ditto is holding an Everstone

Having Dittos of useful natures and holding Everstones help with breeding. You could have a Ditto with Adamant, Modest and Jolly and all those other natures and then breed natures easily. The only problem is getting those Dittos in the first place. Lol.

Regarding the Colosseum bonus disc to get a Jirachi:

How exactly does the process work? Can I keep dumping Jirachis onto the game, or does it only work if I don't have Jirachi in the Dex yet?

Also, can I get a Jirachi onto Ruby, transfer it to, say, my copy of emerald, delete the save game on Ruby, and then repeat to get unlimited Jirachis?

I distinctly remember it being one per cartridge, and it can tell if you start a new save file, but I'm not completely sure. Anyone back me up here?

I know for sure if you DON'T start a new file and just trade it, it won't work.

If I leave the "Battle Scene" off and a shiny appears, will the animation of shiny pokemon be shown? And will the pokemon look normal or shiny? Thanks^^

Battle Scene only turns off the animation of attacks, such as making a wave when you use Surf, or a brown wave when you use Muddy Water.

Battle Scene won't turn off Shiny sparkles, so if you're lucky enough to find a shiny, it'll still look all pretty for you.

Ah, ok, thanks for that. Well, at least it means I'm still unlucky, not for letting a shiny go away, but not for finding one xD

How does the mailing function work in RSE? I know you're supposed to attach Wave Mail on a Wailmer, but what does it actually do? Do you just type text into it or something?

Apart from attaching one item onto one Pokemon and trading, is there another way to transfer many items at a time to another game?

I don't understand the Mail stuff at all, so I can't answer your first question.

However, yes, unfortunately, that is the only way to trade items.

I already have a thread for this but I just want to post it here to make sure.
Since I fixed the berry glitch in ruby with my emerald,in my emerald the clock stops,I couldn't grow any berries and the lilicove lottery tells me to go back tomorrow everytime I visit her,is there any way to fix this?

P.S.I play emerald in gameboy and not in pc

No idea. I've never heard of anything like that happening in Emerald.

Well someone in my topic "can pokemon emerald have the berry glitch" said that he got the same problem too

Maybe I should email pokemon.com about this problem and how to fix it...

Still the berry master doesn't give me berries and the berries I plant wont grow...

does anyone know a good Pokemon to use against the seventh gym in pokemon emerald?

Heh, heh... a well trained Sableye can take out all of the trainers up to Tate and Liza - its immunity to psychic, fighting, and normal attacks means that almost nothing can affect it! Tropius is a good choice for the final battle, but you should watch out for Solrock's flamethrower. Tropius and a strong water-type will do the trick.

And, by the way, what are the stars on the trainer card for? I got one for beating the Elite Four, but i dont know whether i can get more, or how to

You get them for doing the following, in any order:
- E4
- Completing Hoenn dex (first 200)
- 50 wins at BT
- beat all 5 Master contests + get special painting in each

thanks for the advice, I never would've thought of a Tropius