H4-H1B COS and H4 EAD question

I am currently on H4 and my spouse recently got his I140 approved. We are thinking to apply for H4 EAD which as per his employer can take 4 months to get approved. I also have a previous H1B petition for which any employer can do a COS from H4 to H1B as and when I get a project.My question is that if I apply for H4 EAD and that is in progress, meanwhile I get another project for which the employer is willing to do a COS from H4 to H1B in premium processing and that approval comes before H4 EAD approval, what will be my legal status to work? Can it create any complications?

I might get RFE for my H4 EAD case asking to prove my valid H4 status.

If such a case happens and I get my H1 before getting H4 EAD result, can I continue working on H1 or do I have to respond to H4 EAD RFE or that can be ignored?

Both are legal options to work. H-1B supersedes H-4 EAD so if the former comes through, latter must be abandoned. You can inform USCIS that you don’t intend to pursue EAD any longer.