Last action rule - H1B and H4 extension simultaneously for same applicant

USA H1B Visa
1

Hello,

Could someone please explain me how the last action rule determines the status and petition validity in below scenario ?

  1. My H1B and wife’s H4 are valid till Nov1, 2019 and we are planning to apply for my H1B extension and wife’s H4 extension in May 2019.

  2. Also, my wife will be applying for H1B in April 2019. Let’s assume it will be picked in the lottery and ultimately gets approved.

I’m assuming the last action rule is based on the notice date and not on the start date of the petition. Please let me know if my assumption is wrong.

Based on this assumption, what happens in the scenario where wife’s H4 extension is approved after H1B is approved ? Is H1B considered invalid in this case ?

Thank you !