Yes, you can buy stock in NSE and sell the same in BSE or vice-versa but to that, the stock has to be in your Demat account since the delivery of a sell position goes to the exchange separately and the delivery of the buy position will be received from the exchange separately. Example: Intraday scenario: If you have bought a stock today in NSE but intent to sell the same in BSE then you can’t sell since the stock does not exist in your Demat account. Stock are credited in your Demat Account only on T+2 day. Delivery scenario: If you have bought a share today in NSE and have held it until T+2 day that is when the stock gets credited in your Demat account then you can sell the same share in BSE on T+3 day.
Convert to delivery is applicable on Equity Cash intraday positions only. It is applicable when an Investor has entered a position with an intraday order but later on intends to take delivery which is settled on the T+2 basis. Please Note* When a trader is long on Equity Cash then he/she needs to maintain 100% of the Purchase Amount in order to convert an intraday position. Need to have stock in the Demat account - Cannot short a share otherwise for more than a day.