Here are my thoughts on your questions:
a. If you are not currently employed in Australia then place N/A. Further in the form, it would ask if you'd prefer to use your Oz hospital/facility's address for future correspondence so better place N/A if you are not employed yet in Oz. Use your brother's residence address as correspondence, in this way you'd be able to receive letter/s from NMBA sooner.
b. I belive this refers to
qualifications, examinations,assessments related to nursing such as your BSN diploma, board certificate, pitch in your board ratings (specially if impressive), license, post grad educ, trainings and the like as long as they are relevant to nursing.
c. About the indemnity insurance, it is an IF question in the form. But yes it is referring to indemnity which has been explained by cioman. You'd need to read on the exceptions enumerated by the board to shed more light on the matter.
Well, i hope this helps and pray that you will pass the board! Cheers ü
P.S. Anyone,please, correct me if i'm wrong. Thanks.