回複：請問: 我2006年底被公司派回中國工作, 2007年底485被批準,

I had the same situation a year ago as yours. I was assigned to work in China in 04 and returned to the U.S. in late 07. A few things to share with you. I consulted with both American lawyer and Chinese lawyers when I was in your situation.
The applicant must be physcially in the U.S. when 485 is filed. Also One must stay in the U.S. until I received the notice of receipt. I did so. I made a trip back to the U.S. for my fingerprint also. This was what I did in 2006.
I was mostly in China when my 485 was pending. I was in China when my 485 was approved.

I relocated to the U.S. after I had my GC because of family situation. But I am not sure whether it is a "have to" after you have the GC.