because you need better wifi
yes
Yup.
in jubilve city
either by cheating or a wifi event (but wifi event expired)
its the card that enables you to use the wifi station in jublife city.
you just can't
In Jublife City
Via Nintendo Wifi.
The only way to see Palkia in Pokémon Diamond is to use WiFi. Otherwise, you can't.
Yes you can Yes you can
You can trade, battle, and have voice chats with your friends over Wifi in Pokemon Diamond/Pearl, but to do so you need to know your friends' Friend Codes, and your friends need to know your Friend Code.