H4 Cannot Work Legally
US immigration law works on the basis of physical location of the person. If you are working from USA without an H4 EAD permit, it is considered illegal irrespective of where you get the payment for your work.
But, it is probably difficult to track. Talk to your employer. If they are a big entity, they will not agree to it either.
So, use your best judgement.
Processing time for H4 EAD after Biometric
It is taking anywhere between 3-6 months for H4 EAD to get approved after biometrics.