Jio Platforms made a strong stock-market debut on Wednesday, opening 21% above its issue price even as the Sensex fell more than 1%. The key test now is whether the issuer of India's largest initial public offering (IPO) to date can hold that premium through the close, unlike India’s five largest previous debuts. A Mint analysis shows that none of those five predecessors gained more than 2% on day one, and three ended below their offer prices.