Hey there! If you pay your credit card bill using IDFC First debit cards, you won't earn FIRST rewards points Directly. The rewards points are typically earned on purchases and transactions, not on bill payments. (Source: Conversation with Gemini AI) But, I personally use third party apps for CC bill payment like Cred, Mobiwik(mostly).
As I spend using my CC in such a way, so that none of my card has TAD of >₹5000, thus confirming assured cashback of 1% via Mobiwik(multiple a/c) and also able to maintain healthy Credit Score