I have 2 questions: 1. How do I give my Chao custom names? and 2. How do I evolve my Chao into a "Dark Chao"? Thanks.
1. In SA2 for DC, you can change a chao's name through the VMU. If you're playing SA2B, take it to the Fortune Teller in Chao Kindergarten. When she asks if you want her to choose a new name, say no, and she'll offer to let you name it yourself.
2. Treat it well with Shadow, Rouge and/or Eggman (pet it, feed it, rock it, etc.) and give it Dark Fruit. You could also beat it with Sonic, Tails and Knuckles to make it into a Dark chao, but that's not a good idea if you want your chao to reincarnate.

~ Crazy C Lea