Hehe.

1) Those are called spurs. They are the remains of the legs that they used to have waaaay back, but evolution has caused snaked to lose their legs.

2) I'm not sure, but it just looks to me like it's just a discolouration of a scale.

3) That is urate. It is one of the 3 waste items that snakes discard. Urine, Urates (accompanied by urine) and Feces.