H1B转H-4，10.10离开公司, LG's H1 starts 10.1，什么时候递交539?

如题，10月10号是正式离开雇主的日期，LG现在是F1(OPT)，H1B 10月1日开始生效。
I539已经准备得差不多了，现在就可以寄出去，还是要等到LG的H1差不多开始了，再递交转身份的申请？有点担心他们开始process的时候LG还是OPT，会不会有问题。

另外I539 part 3g
"Have you, or any other person included in this application, been employed in the United States since last admitted or granted an extension or change of status"

我上一次入境是H1B，我这个问题是不是应该答yes，然后补充说
I was employed by xxxx located at xxxxx with monthly income of yyy. The employment was approved by USCIS with receipt number (当初H1B的申请number)？

多些各位老师！