If you are researching someone for legitimate safety reasons (e.g., investigating a catfish or scammer), do not try to break their privacy. Instead, use Open Source Intelligence (OSINT) to gather public data:
Since 2018, Instagram has strictly limited its API, ensuring that third-party applications can only display content from a user's own authorized account. This makes "unlocking" a stranger's private profile via a website technically impossible through legitimate means. Common Risks of "Free" Private Viewers free instagram private photo viewer