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.
in jubilve city
because you need better wifi
In Jublife City
either by cheating or a wifi event (but wifi event expired)
WIFI connection and then put happy together. GOT IT PAL!
Yup.
in jubilve city
yes
because you need better wifi
Via Nintendo Wifi.
In Jublife City
you just can't
its the card that enables you to use the wifi station in jublife city.
either by cheating or a wifi event (but wifi event expired)
Of course you can. I played my Pokemon Diamond with my cousin that has Pearl.
no wifi
You cannot.