L1B to H4 COS + H4 EAD

USA L1, L2 Visa
1

I am on L1B and my spouse has i-140 approved. Can can I do L1 to H3 COS and file H4 EAD all together. I read in forum that we can file both application in parallel. But questions is:

  1. Do I need to send both applications (i-539 and i-765) in separate postal packets?
  2. If separate packages, then what evidence shall I attach with i-765 to apply EAD, This time I will not have approved H4? because in Question no.15 (form i-765) - “Current Immigration Status” is L1B.
  3. My child is on L2 (Dependent). Can I fill one i-539 for both me and child? (defiantly I’ll send separate checks for fees).