Is the I-797C, Notice of Action different than the case approval?
I only received one receipt while I applied for my 3 children, can I ask USCIS to send the other 2 receipts again?
My I-130 was approved can I apply and pay for NVC although my PD is September 16 2013 which is not current??
Please see this link from USCIS for first question: http://www.uscis.gov/portal/site/uscis/menuitem.5af9bb95919f35e66f614176543f6d1a/?vgnextoid=9d4f068d9c456310VgnVCM100000082ca60aRCRD&vgnextchannel=db029c7755cb9010VgnVCM10000045f3d6a1RCRD
The USCIS receipt are based on the form submitted. Each form will typically have one receipt.
For second question, please see this: http://blog.mygcvisa.com/2013/09/nvc-consular-processing-steps.html