If you mean the wifi trading, that would be every pokemon, otherwise, there is no answer to that, but there will probably be a celebi event with any luck, and maybe mew. These are just guesses.
Mew was only available with a wifi event from October 15th, 2010 to October 30th, 2010.
until July 16 2010 you can receive jirachi by going to mystery gift and receiving via WFC(must have wifi connection)
There is a wifi trade option available in every pokemon center after a certain amount of progress through the game. The Global Trade Station (or GTS, for short) is in Goldenrod city.
only by the event of celebi that is going to be send by wifi connection
You can't get WiFi in a Pokemon game on a PC.
only when available in wifi or at some place OK
You have Wifi battles in the bottom level of the Pokemon center
You don't. pokemon saphire was made before wifi existed.
You need a wifi router or a Nintendo wifi usb
Any where that WiFi is available. There are no restrictions.
Yes, there is wifi available in Sudan.
You can't catch mewtwo in Pokemon diamond because its not available in the game. if you want it you either get it by a friend or a wifi event which i seriouscly doubt.