It evolves Porygon to Porygon2 when traded.
you have to have a upgrade and then trade it
You can't yet. Sorry.
go to oaks house after national dex complete
You have to buy Pokemon Platinum. (Its a separate game!)
look for it in both team galactic buildings
The Pokemon Platinum update for My Pokemon Ranch is only available in Japan for Japanese games.
I believe you can can find an UpGrade(used for evolving Porygon into Porygon2) in the Eterna City Hideout.
Get the Upgrade from one of the Team Galactic Hideouts And then to make a Porygon Z get the Dubious disk from another one of ther hideouts
you give porygon the upgrade then trade it to get a porygon 2 then you give your porygon 2 another upgrade and trade yet again to get a porygon-z
In the wild or from professor oak
You can only get porygon-z if you trade a porygon2 with an upgrade item only in pearl platinum or diamond version.
The Pokemon is poregon 2 and you trade poregon wile it is holding a upgrade.