I am a postdoc in USA, doing research on infectious diseases. I got MD and PhD in my home country. Last week, I got my Green Card based on National Interest Waiver (NIW). My questions are as follow:

1. Before changing a new field (become a clinical physician) or running a bussiness (open a firm), how long am I required to continue to work in the field of my NIW claim after Green Card?

2. I want to do medical residency training (3 years) and become a clinical physician (purely clinical work, not involving in research). Will USCIS revoke my Green Card if I follow medical residency training and become a clinical physician?

3. After my postdoc position finishes (next 2 years), let say, I can not find a new job, will USCIS revoke my Green Card?