Millennia and SBI Cashback doubt

If I purchase Amazon, Flipkart GV's directly from their apps, will I get 5% or 1% on Millennia? Same doubt for SBI Cashback as well. What will be MCC? Any better way to buy Apay GV's, ASV's. I have Apay ICICI+ prime shopping edition and following cards

Sapphiro, Coral Rupay, HPCL coral

FK Axis, MyZone, Neo

Millennia, Neu Plus

BOB Select, Snapdeal

Simply Save 

Stanc Platinum rewards 

one Card Federal

Planning to take one more SBI card which card is best? Cashback card not eligible for instant discounts, thinking about BPCL Octane for both petrol purchase and online sale benefits. is it good idea