No it is not possible. You have to hack or trade.
You can if you use action replay :P If you don't use one, then it is impossible to complete without trading as there are only certain Pokemon that can be caught in diamond and vice versa with diamond.
Trading.
You can't catch Lugia in Pokemon Diamond. You can only get it through trading or cheating.
You can not find or get manaphy on Pokemon diamond but you can by hacking, trading or... if you have Pokemon ranger you have to complete the manaphy mission and then you can put it onto diamond.
there is actually no finish to Pokemon diamond as you can keep trading and catching Pokemon. however, the actual storyline finishes when you become Pokemon champion.
All 150 pokemon are in the game so you dont have to trade for them. BUT IT IS EASYER
You can if you use action replay :P If you don't use one, then it is impossible to complete without trading as there are only certain Pokemon that can be caught in diamond and vice versa with diamond.
Only by trading from Diamond. In Pokemon Pearl you get Palkia and in Pokemon Diamond you get Dialga.
It is not possible to catch a wild Turtwig on Pokemon Diamond. It is generally impossible to find and catch Starter Pokemon in the wild. This was a mechanic designed to encourage player interaction for trading.
You can get a Cyndaquil without trading only by transfering it from a GBA Pokemon Game onto your Pokemon Diamond Version.
You can't.
Trading.
yes.
You can't catch Lugia in Pokemon Diamond. You can only get it through trading or cheating.
By trading machoke.
You can not find or get manaphy on Pokemon diamond but you can by hacking, trading or... if you have Pokemon ranger you have to complete the manaphy mission and then you can put it onto diamond.
there is actually no finish to Pokemon diamond as you can keep trading and catching Pokemon. however, the actual storyline finishes when you become Pokemon champion.