NIW dependent 收到485 rfe

Please submit proof of your continuous employment authorization in the U.S.
from xx-xx-xx to the present. Such evidence may include copies of:
Employment Authorization Documents (Forms I-688 or I-766) granted to you by
this Service;
Form I-797 approval notices, showing you were granted status in an
employment-authorized nonimmigrant classification; and/or
Copies of Form I-94 Arrival/Departure Records showing you were admitted to
the U.S. in an employment-authorized nonimmigrant status.

去年底到今年4月份之间在原公司请假，H1B/unpaid leave，4月份用EAD换工作至今。
请问：
1. 为什么dependent还需要proof of your continuous employment呀？
2. 我原来的HIB日期到今年6月底，因为我用了EAD, H1B已经失效了吧？可以作为proof
吗？
3. 什么是Forms I-688 or I-766？
4. I-94 Arrival/Departure Records。用护照上的I-94还是H1B上的?
谢谢！