1）我是不是可以理解成，如果兒子能夠在母親的非法居留時間少於180天的情況下提出綠卡申請，那末回美證就可以和綠卡一起申請？
-Yes. She can use AP to travel as long as her unlawful presence is less than 180 days when she files I-485.
2）如果母親黑下來了，兒子還沒有來得及給母親申請綠卡。因為特殊原因母親需要回中國去然後母親就回去了。那末母親就有在美國非法滯留的曆史。以後在簽證問題上母親就會有你所說的3-year or 10-year bar。但是當兒子拿到公民後，給在中國的母親申請綠卡，這個曆史汙點會影響母親的綠卡申請嗎？
-Yes. As long as her unlawful presence is less than 180 days when she files I-485, she will be sujected to 3-year or 10 year bar if she leave US before she gets her green card. It is less than 180 days, she will be OK to get the immigration visa in China.
3）如果母親黑下來了，兒子也已經開始了母親的綠卡申請。因為特殊原因母親需要回中國去然後母親就回去了。那末這已經開始的綠卡申請會出現什末問題？
-Same answer as for 2).
