What is the timeline to reply to mail from US Consulate?

I received 221g for going for stamping with h1b amendment in progress and with old I797-B.Now today i got a mail from US consulate asking for the I797.But i have the I797 C which is only the receipt notice.Waiting for amendment to be approved.

can i send the I797C?

or else i have to wait for another 2 months to get approved I797 and then only i can reply to the US consulate mail.Is it fine to wait for that much time?