H1 + COS F1 OPT to H4 + H4 EAD

[anitk]

Hi,

My spouse's I140 is approved recently.His employer is filing for H1 extension based on I140. Im currently on  OPT EAD valid till MArch 2019. Can his employer file for H1 extension + my COS  F1 OPT EAD to H4 + H4 EAD together?

Should I stop working as soon as USCIS receive my COS application or can I work till I receive COS approval?

Will COS approval  and H4 EAD be processed simultaneously or will there be any delay between these two?

Thanks in advance