no
A good team needs varies of types. My team are Infernape, Dialag, Floatzel, Luxray, Weavile, and Staraptor. The types are Fire, Dragon, Steel, Dark, Electric, and Flying. That means my team can beat Grass, Dragon, Water, Fighting, Bug, Ghost, Psychic, Poison, and Dark types.
Both Pokemon Diamond and Pearl have Team Galactic as the main antagonist team.
A good team for Pokemon diamond or pearl is probably Empoleon, Staraptor, Roserade or, Steelix, Machamp, and Haunter or Gengar.
I don't know because you didn't type in a team
what do you mean after 245 days?
That's a good team
You can't join team rocket in Pokemon diamond. Actually team rocket is not on the game
There isn't a way you can get a full good dragon type team without trading unless you want more than one of a specific dragon Pokemon being either Kingdra or Dragonite.
any high level Pokemon like an inferape with flame wheel
Torterra, Empoleon, Infernape, Garchomp, Luxray, Snorlax
yes
you can start making a good team by raising all your Pokemon not just your starter i hope i hellped