Gym leader Roark has one in the orebrough gym.
craniados, sheildon, and some more after the elite4 (aerodactyl, anorith, omanyte, kabuto, ect.)
no nobody in Pokemon platinum have a doexys.
no
No
yes grass type trainers do
battle trainers or catch the Pokemon
Craniados
Sadly, you can't/
There are no trainers in Pokemon platinum with phione. if you want phione use action replay.
beat alot of trainers
someone on route 222
no you can't (sorry)