What is the forex markup fee on Indian credit cards?

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.

Dispute process that worked for me: I called customer care within 24 hours, raised a dispute via the netbanking portal (uploading the receipt showing I never visited the merchant), and got a provisional credit in 5 working days. Permanent credit came after the bank's investigation in about 30 days.