I didn't receive cash back for subscribe and save products on my SBI Cash back card. I think you will not get cash back for auto debit kind of transactions. You will get cash back for Auto debit/E-mandate transactions with Amazon pay ICICI card.
Better way to purchase Amazon yearly prime membership is just acess rewards marketing lounge in this website.
Few sellers will give the membership voucher for 1100 Rs - 1200 Rs.
Or else if you or your friends has select debit or credit card then you can redeem the Amazon yearly prime membership just for 1 Rs.
You can try buying the Amazon Prime GV from Magicpin using SBI CB CC. Magicpin gives a 10% discount + 5% cashback on CC. Did the exact same thing this week and received cashback