多谢8老师的回答。又惊出了一身冷汗。现在分析，律师的做法确实是利用了CBP officer的错误。
-The lawyer actually does not understand the L1 rule. Like H-1, L1 petition has two parts, one is the petition approval which allow the employer to hire a foreign employeee (like you), another is the empoyee's I-94 which allows the foreign employee legally to work for the employer. Both of these two have to be valid at the same time, thus the foreign employee can work for the employer. In your case, due to the USCIS/CBP mistake, you have the extended I-94 duration longer than the L1B approval expiration date. Thus, actually the L1B petition approval was not valid, and of course you can not work.
我现在的方案是：
1. 由于I94,没到期，所以我可以停留在美国，但要求公司立即停止我的工资发放；
2. 律师提交材料，extension我的L1B状态。我的美国等待结果。
-You can ask the employer to use preemium processing to get the L1B extension results in 15 days. If the approval has a new I-94, then you can continue to work. If it has no I-94, then you may have to go to China to get the L1B visa to come back. Talk to a goo dlwyer.
现在会出现的问题：
1. 我上面的方案是否合法？会不会被移民局认定非法滞留？
-You are out of status, but you may not considered as unlawful presence due to your unexpired I-94. Thus, you may not have trouble to get the visa in China (if you have to get it there).
2. 如果extension成功，我是否就可以立即在美国继续开展工作了？还需要回国申请Visa吗？
-See my above answer.
这420天会不会缩短以后L1A的那2年时间？
-No. The 420 days is for you to make up to total five years of your L1B (i.e. you actually have not used all of your five years of L1B yet at this point).
By the way, I don't know whether yrru absence of 420 days was continuous (e.g. your stayed in China for > one year during the L1B). If yes, you may be qualifed to reset your L-1B clock for another five years from the date of your last entry. You may consult a good immigrtant lawyer.
3. 如果extension失败，那么我就必须要离境了吧？在等待extension的这段时间会不会被认定不合法，非法滞留？
4. 如果extension失败，我需要怎么办呢？回国停留一年，再申请L1A？还是凭借i94时间停留在美国，refile申请L1A？
-The L1B extension petition will be approved, but it may have I-94 or may not have I-94 because you are out of status, techincally. See above.
