-Yes, as long as you file your H4 application before your OPT到期 (12-16-2008).
2)如果OPT 過期時OPT extension 仍然pending,我能拿到臨時EAD嗎?如果能拿到臨時EAD, 但之後OPT extension被拒,我若沒申請H-4,是否也必須立即離開US?
-What does 臨時EAD mean? Only if your OPT extension is approved, you can receive the EAD based on OPT. If you do not file I-485, you can not apply for the EAD based on I-485.
3)若能同時申請OPT延期和H-4, 是否哪個先下來哪個先生效?
-Your final status will be decided by the last approved application.