There are no additional playable characters in Shadow the Hedgehog. He's all you get. The other characters will join you in each level as a support character, but you don't get to manually control them.
knuckles
eggman ,eggman's robots and shadow the hedgehog
yes shadow the hedgehog was created by eggman
there's quite a lot but ill name some Dr eggman, shadow, knuckles, hammerhead, rough etc
I wouldn't go as far as using the term friends, more like allies.
shadow the hedgehog was created by Dr.general robotnik. He is eggman's grandfather. shadow was created in the space colony ark.
You have to get a nude picture from Eggman.
Knuckles gives you a video transmission from Eggman saying that he will trade the Chaos Emerald for Elise. His base is at White Acropolis which you can only access from the Soleanna city district. Once you beat the action stage, Sonic, Tails and Knuckles reach Eggman, only to be sent to the distant future. There, Shadow and Rouge is waiting for you.
No, they are not related. Shadow was created by a relative to Dr. Eggman.
No, Shadow the hedgehog was created 50 years ago by Dr Eggman's grandfather, Professor Gerald Robotnik.
Shadow the hedgehog does not have a mom, Shadow has a creator named Dr. Gereld Robotnick, The Great Grand Father of Dr. Eggman.
Professor Gerald Robotnik(Eggman's grandfather)