Comment on POA - Power of Attorney for your Demat account
1. You will have to pay DP charges to HDFC, I think they charge Rs 25 or 0.04% of the transaction whichever higher.
2. Yes, you will be able to buy from both Zerodha and HDFC SEc
3. No AMC for trading account at Zerodha. No charges for web/mobile. Call n trade, we charge an extra Rs 20 per executed order.
4. Transferring into the trading account via the payment gateway has Rs 10 in charges that is paid to the Payment gateway provider, while withdrawing there are no charges.