In Indian Stock market, Can I place a limit order to buy a stock below 25% of current market value as Good for 6 months on HDFC Securities platform?
In general, theoretically you can submit a limit order with a good-til-cancelled time-in-force to most stock exchanges, but in practice there are limits preventing you from doing exactly that.
Some brokers put boundaries on the time-in-force such as setting the maximum time to three months (rather than the 6 months you desired). Part of the rationale is that there may be events that would effect the stocks price such as dividends and it is difficult to predict these more than 3 months away, so they require that you positively update the order for it to continue to remain active for another 3 months. They may also cancel or adjust the orders in the event of a stock split or when the exchange undergoes maintenance.
However, many exchanges nowadays perform order checks, so if the price of the order is too far away from the current market price, then the order will be rejected. Usually this is when the order is to far in the market (e.g 25% above the bid price) but there are usually boundaries on both sides.