You can get Gold, Silver and Crystal Pokemon by trading them with either FireRed or LeafGreen, then trade those Pokemon in FireRed and LeafGreen with your Emerald. Or after you've defeated the League go to the Safari Zone and the area that was blocked off, can now be explored, it has Johto Pokemon to a certain extent.
No there is no way of transfering from Crystal to Emerald. Only RBY to GSC, and Emerald to all games beyond.
You can get Pokemon from the Honnen and Kanto region, and after beating the Elite Four you can get certain GSC Pokemon.
gsc stands for gold silver and crystyl because they are all Pokemon games so gsc Pokemon are all Pokemon from Pokemon gold Pokemon silver and Pokemon crystyl and there it is you know the answer forever.
Reach 200 owned on your national dex and Prof. Birch will give you a choice between the three GSC starters.
Gold / Silver / Crystal
Unfortunately you can't. The Pokemon creators decided they didn't want to put that into RSE games. I think it was because all of the glitches such as the mew trainer glitch in RB and the bad egg glitch for Celebi in GSC, that's my guess. Hope this helped :)
Same reason you fight Red in GSC.
its not an emerald its RAYQUAZA the main legendary Pokemon in Pokemon emerald.
The population of SG-GSC is 12.
GSC Systems was created in 1984.
You cannot get a Yanma in Pokemon Emerald, as only Hoenn Region Pokemon can be found in Pokemon Emerald.
There is no PalPark in Pokemon Emerald.