What is the minimum credit score required for premium credit cards in India?

On the add-on card: yes, the primary cardholder is fully liable for all spends on the add-on. There is no separate credit limit or statement. So only issue it to someone you trust absolutely — spouse, parents. Not friends, not siblings you have money disputes with.

For the fee waiver condition: most banks count only retail purchases, not EMI, wallet loads, or fuel (in some cases). Read the TnC PDF linked at the bottom of the fee-waiver email — it's usually 2-3 paragraphs of fine print that change everything.

Yes the rewards sound amazing in marketing, but the redemption catalogue is full of products at inflated MRP. The statement credit redemption is almost always the best value. Skip the merchandise, skip the flight bookings, take the cash.