In the south, on the left hand side of the road.
Bottom left.
in eterna city the house at the bottom of the city on the west.
Prof. Oak in a house in Eterna City.
in eterna city
Prof Birch is NOT in Diamond Prof OAK is in Eterna City.
Once you get 35 Pokemon in your PokeDex, Prof. Rowan's aid will give you the Exp. Share in Eterna City's gatehouse.
Professor Oaks house is at the bottom of Eterna City. As I should say... Next to the Gym I hope this helped
You must have the National Dex to get the Up-Grade. Go to the Pal Park and Prof Oak will be there. He will say he is staying in Eterna City. Go to Eterna City and walk to the South - Western house. Talk to Prof Oak again and he will give you the Up-Grade to Level up your Porygon to a Porygon 2
By Prof. Oak in Eterna City after visiting him at Pal Park.
After you obtain the National Pokédex and visited the Pal Park, Professor Oak appears in the southernmost house in Eterna City.
After you get the National Dex, talk to Prof. Oak in a house at Eterna City. He will give you the Up-Grade to evolve Porygon to Porygon2 through a trade.
He is at the bottom left corner in a house near victory road.