You can't.
No. The maximum of Pokemon to carry with you is 6. I suppose it's the same with the new Pokemon game for the DS, Pokemon Platinum.
I believe that Pokemon platinum is better than diamond and pearl because it offers more features, and allows you to do much more cheats and tricks and get more Pokemon through normal game play than Pokemon diamond and pearl. Yes, it is.
No
yes when you get the national dex
you don't.
no
Platinum has more Pokemon 247 than DP and DP has the same amount of Pokemon 151
in your box yes but not in party.
I'm Sorry but you cant get more than 18 boxes in Pearl/Diamond
Pokemon Pearl is in generation IV and is in the Sinnoh region. Emerald is in generation III and is in the Hoenn region. You can catch way more Pokemon in Pearl than Emerald.
The trade-in value of Pokemon Pearl varies in different stores. An estimate would be no more than 10 dollars, in the United States.
no you can not. its one and that's it. ONE