GTC orders which are not sent to exchange will be available for modification. You cannot modify GTC orders sent to exchange or when it is in active status. To modify price you can cancel the existing order and can place new GTC or normal order.
How do I modify or cancel an order?
Can I place a limit order as AMO?
What are the order types available and where do I find them?
For cover orders, till what time can I square off my open positions manually?