Cash on Delivery (COD)

What is Cash on Delivery?
Do you support COD (Cash on Delivery)?
Is COD available for any amount, Do you charge extra cost?
How does COD works?
How long COD will take?
Can I pay COD person through Cheque/DD/Debit, Credit CARD ?
Do you provide lab certificate with COD?
Will COD person call before coming?
Can I open the packet before paying the money?
Can I track my Cash on Delivery shipment online?