H4 standalone transfer after H1b transfer is done

Hello,

Currently, I have an H1b amendment + extension in progress and my spouse is in India and will use the Dropbox facility to get her visa stamped based on H1b amendment approval and use that approval at CBP to get new dates on the stamp.

Now, I have another offer from a different company and I am willing to join that.
I am not travelling and I am willing to start H1 transfer process and wait for my wife to return until I join so that the entry at CBP can be smooth.

My spouse has a job here and has an EAD which expires early next year

Question:

Can I start with H1 transfer and file an H4 transfer once my wife is back?
Can H4 transfer be done with premium processing as a standalone application along with H4 EAD?
If not premium processing, what would be the average delay in H4 transfer and how does that effect the EAD application? Can she still file with the new revised dates based on the H1b stamp with which she entered?

What could be our best strategy here?

Appreciate the help on this matter.

Yes. However there is no transfer for H4 as H4 is not employer dependent. It is rather a derivative of primary H1B so in case of H4 it is only a extension of status based on the H1B change of employer aka transfer petition.

Yes, however there is no premium processing for H4 at this point however this will soon be available.