-they have to file their H-4 extension before their H-4 status expires, for example, in March 2009, but only can extend their H-4 to 明年8月份 if you can not file your H-1b status extension together with theirs at the same time. Their H-4 status extension can be filed separately from yours and they can do it by themself.
If your H-1 extension is filed along with your family H-4 extension, your company can do the paperwork together, but please keep in mind their H-4 status extension has nothing to do with your company.
[2]。 我本人的H-1最遲應該在何時提交移民局更新??
-You can only file your H-1 extension in advance <120 days before your H-1 status expires.
[3]。 提交期間能否回中國??
-Yes. But only little risk is that if your H-1/4 extension is denied during your travel in China, you will have trouble to come back. Of course, this is immpossible to happen if you just stay in China for a short period of time.