the best Pokemon to pick at the start is PIPLUP or CHIMCHAR
There are all pretty good Pokemon but my opinion is Chimchar. He evolves into fire/fighting type.
You cannot find a Charmander on Pokemon diamond. You have to get it from Pokemon Fire Red or Pokemon Leaf Green. Charmander is a starter Pokemon, so you don't have to catch it.
As Totodile is a Generation 3 starter Pokemon, it cannot be obtained directly in Pokemon Diamond. Instead, players have to transfer it via trades from previous generations of the Pokemon games.
Chimchar is a starter pokemon so you can choose him with Barry at the beginning.
your question Doesn't make any sense , you can't change the 3 starter Pokemon. and what is "this a cheat" mean? use action replay to change starter Pokemon into what you want. you might need pokesav.
Chimchar
piplup is the best starter pokermon piplup is the best starter pokermon --------------------------- I chosed Turtwig grass type
The starter pokemon for Diamond and Pearl are Turtwig, Piplup, and Chimchar.
in order from best starter to worse Piplup Turtwig Chimchar
you can get it as your starter Pokemon
piplup
Choose it as your Starter Pokemon.
You have to choose it as a starter
I'm pretty sure that the only way to get another starter Pokemon in Pokemon diamond is to go to the Global Trade Station (GTS) and trade with someone.
A level 60 or up starter Pokemon dialgua or palkia and any Pokemon over 60 just not graveler
Turtwig in Pokemon Pearl and Diamond.
you get piplup as a starter in Pokemon diamond/pearl/platinum