The short answer
Do not rely on Incognito to hide an Instagram story view made while signed in. Private browsing concerns the browser session on your device; it does not instruct Instagram to treat your account as anonymous. If avoiding an identifiable interaction matters, do not open a story under the assumption that the private-window icon is protection.
What private browsing actually changes
Chrome opens a separate session and limits the browsing information retained after you close it. Websites can still receive requests and collect information. Signing in identifies your account to that website. Deleting local history or closing the window afterwards is not proof that a service-side action was erased. Downloads can also remain on the device. Google Chrome.
No login does not guarantee access
A logged-out Instagram page may ask you to sign in or may not expose the story at all. Refreshing in another private window does not give access to a private profile or a restricted audience. A VPN is not an Instagram logout button either: changing your network connection does not remove an account from an authenticated session.
How the InstaLenso route differs
InstaLenso prepares a public profile username and lets you continue in Telegram without entering your Instagram credentials. This is a different request path, not a special browser privacy mode. Media availability is determined by the bot response, not by accepting the username. Telegram and the service still process interactions; there is no promise of invisibility to every party.
Avoid testing on someone else
If you want to compare viewing methods, use accounts you control or a consenting test partner. Note whether you were signed in and exactly which action you performed. A profile preview is not the same as playing a story. Treat an inconclusive test as inconclusive, and do not use airplane mode, later blocking or cleared history as a guaranteed way to undo a view.
Instagram viewing and download tools
Anonymous Instagram Story Viewer