Sideloadly is currently the most reliable tool for installing IPAs on older iOS versions. Connect your device to your computer via USB. Open Sideloadly and drag the Instagram IPA into the tool. Enter your Apple ID (to sign the app). Click "Start."
Never enter your Apple ID password into a third-party tool like "Cydia Impactor" unless you trust the developer. Use a burner Apple ID if possible. Instagram Ipa Ios 9.3 5 Download