According to instructions, send application to Sydney NS. You will indicate on your application if you want it processed in Buffalo or China and they will forward it to the appropriate visa office if you qualify.
When you look at the 2 different addresses, you see that the first is a PO box and the 2nd is a street address. Also the 2nd says "courier address" at the top. If you mail your application, you use the first address with the PO box. If you have a courier deliver your application such as fed ex or ups, use the "courier address" so the courier knows where to go.
When you look at the 2 different addresses, you see that the first is a PO box and the 2nd is a street address. Also the 2nd says "courier address" at the top. If you mail your application, you use the first address with the PO box. If you have a courier deliver your application such as fed ex or ups, use the "courier address" so the courier knows where to go.