I have couple of general questions about approved I-140 and H4 EAD. Could you please provide clarification.

1. Once my I-140 is approved, if I change my employer through H-1B transfer before 6 months of I-140 approval, is my I-140 with old employer still valid (Given old employer didn't revoke the I-140)?

2. If it is valid, while am working with new employer on H-1B, can I use that I-140 from old employer to apply for H4 EAD to my spouse?