Attending H4 visa while previously on H1

Earlier I was on H1b and went for visa extension stamping, unfortunately it get approved. My family is back in US and needs me to join ASAP. If I plan to go for a H4 visa interview now, do I need to put a resignation to my current employment? and should I carry any letter from my employer showing that I am no longer associated with the company?
My only intention to get back to US and be with my family. I don’t have any plans to work while I’m in USA. If I want the VO to believe my intentions, could you please let me know how should I approach?

I am assuming your spouse is in the US and on H1B so you qualify for H4?

You might be eligible for dropbox based on the new policy as you hold H1B visa in past.

Yes, as you will no more be working for your H1B sponsoring employer once you enter on H4 in the US.

I don’t think this is needed. You can carry copy of resignation letter.

You should just state the facts. If you are asked why you are applying to H4 visa when you have H1B, you simply need to state the facts on why you intent to switch to H4.