What are the medical benefits of botox, curare, neostigmine, atropine?

Very broad question. You have asked a very broad question and therefore difficult to answer.
Nature to medicine. Some of these are products naturally found in our environment which are derived from bacteria or plants which have toxic and potentially lethal side effects but in controlled doses have been used for desired medical and cosmetic purposes.
Myriad. Too open ended a question to answer in 400 characters. Each of these meds has very different indications and actions. More specific question?
Not enough space. Unfortunately there is not enough space here to discuss such a broad topic.