H4 EAD after spouse on I140 changes jobs

[PVS]

Hello

Thanks for your concern and taking time to answer this query.

Say my spouse has an approved(over a year) I140 with ex-employer. Spouse joins a new company - company B who would start the GC process again.

Can I get my H4 EAD right now, immediately after spouse joins company B ?

(or should I wait for company B to start spouse's GC process again - LC-PERM-I140, the long process and only when spouse reaches I140 stage again with the current employer - company B)?

in short, would I be able to get my H4 EAD based on spouse's I140 with previous company?

and question 2. how long does H4 ead take?

Thanks for your time again!.