Currently, backtesting on Trendlyne uses the list of constituents as of the current day, rather than the historical ones. 

To approximate historical selections, you can use a filter based on a high market cap. For example, selecting "All Stocks" and sorting by Market Cap lets you focus on top stocks without relying on predefined indices like the Nifty500.

This approach can help simulate backtesting on historically larger companies, even if the exact historical index constituents are unavailable.