HDFC 2500 wala account is for Farmer, so don't expect pre-approved offers from them.
I have some friends who opened that account, it has been more than 6 months they haven't got any offers for credit card.
They got Millenia DC in instant kit so they are enjoying 400 cashback every month. That's it.
Maybe you get pre-approved after few more months, but you shouldn't expect much from farmer's account.
Open 10k Regular account you will get moneyback for sure within 3 to 6 months.
Or open Digi Save Youth 5k MAB online
You can close account after getting the card.