How to get live option chain data in Excel

Open the option chain on the NSE website, choose the index or stock and the expiry, and use the Download (.csv) link above the table. Open the file in Excel. You get every strike's OI, change in OI, volume, IV, LTP and bid and ask at that moment. It is free and accurate, but it is a snapshot: to see a change you download again.

Not reliably. Data > From Web in Excel, or Power Query pointed at the NSE page, often fails or returns nothing, because NSE serves the chain through an API that expects browser cookies and rate-limits automated requests. Scripts that work one week tend to break the next. Scraping is also against NSE's terms of use.

Use a broker API. Most Indian brokers offer one (Zerodha Kite Connect, Upstox, Dhan, Angel One SmartAPI, Alice Blue ANT and others), some free and some with a monthly fee. A small script or an Excel add-in fetches quotes and OI for the strikes you list and writes them into cells every few seconds. You need an API key and some comfort with code or with the add-in your broker supports.

Usually not. People build Excel sheets to add things the exchange table lacks: percentages of the top OI, highlights, PCR per strike, support and resistance, and a record through the day. An option chain tool like AOC already does those, live, with the intraday history kept for you. AOC does not export to Excel; it replaces most of the reasons for building the sheet.

Excel is still the right tool if you are researching your own indicator over months of end-of-day data. For that, the NSE bhavcopy files are the better source.