1. If you hold SBI debit card then you can use SBI Unipay to pay your CC bills, it will give you reward points which you can redeem on sbi rewardz (100 rupee = 1 point, 1 point = ₹0.25/-). In simple terms: 0.25% cashback.
(SBI restriction:
1L per transaction = 250 cashback
10L per month = 2500 cashback)
Ps: There are few threads regarding the cashback on CC bills, you may have a look for better options.
2. Yes, its actually the most expensive debit card of HDFC (850 + GST is the price for a year). If you are saving max user in HDFC then its completely free for you.