Limits on purchase in a billing month for the cards that I know. Better tabulate this too.
- SBI Cashback - Confirmed(5%) - max as allowed by amazon
- HDFC Millennia - Confirmed(5%) - 20K
- Jupiter Edge+ - Confirmed(10%) - 5K
Also note that it's safe to buy ~10K pm via CCs on amazon else amazon puts a block on cc for few months.