Please provide answers and sources for answers

1. Does an alien need an advisory opinion or consultation letter before she can apply for the O-1 visa?

2. List the requirements for support personnel to qualify for an O-2 visa.

3. What is the duration of stay for a P-3 visa?

4. If an alien indicates that he or she was widely recognized but no longer works in that field of endeavor, can he/she qualify for an EB-1A visa?

5. List the persons who may qualify for EB visas.