[Updated – After successful purchase on April 29th Sale]
Flipkart is not allowing same user to purchase multiple device. If you are going for second purchase , It is better to create a new account (with another mobile number and email ID) and proceed following steps with new account.
Make sure that you verify the email ID and mobile number for the account, before the sale itself.
[Optional] Also before the sale go to some other product page and give postal PIN code, so that PIN code will be set before the sale.
Follow these steps then :-