H1extn+H4(COS)+H4EAD- change of status

My Wife H1 extn (i140 approved) is filed in July and received receipt on July 21’17 in regular processing. My H1 got expired so my company filed H1->H4(COS) depend on my wife H1 extn application. My company also filed for H4/EAD.

Question: 1. My wife H1 extn application is still pending for approval in Vermont centre. Any idea how long would it take. Does my H1->H4 (COS) depend on my wife H1 extn application? Mine is filed in California centre as seperate.

  1. If we decide to go for H1 extn as Premium processing, my H4 (COS) will be approved too and EAD as well?