URGENT!!!!!

Hi, I have several questions.
1) Can the employer apply for a S2 type for my sister while applying for a working Z for me? Im the same application
2) Will she need to go out of the country and be back to our country (if possible to any other country please let me know) to get another one again?
3) Will she have to stay in China for those 6 months and not get out of China or there is some number of exits and entries allowed?

Thank you beforehand!