Instagram’s API does not support programmatic login using a saved username and password due to strict security and privacy policies. OAuth 2.0 is the only official and supported method, which requires explicit user interaction for authentication. Attempting to bypass this flow by storing credentials and automating login violates Instagram's terms of service and may lead to API access being revoked.

Instead, you should authenticate the account once using the standard OAuth flow, obtain a long-lived access token, and securely store it (e.g., in a database). You can then use this token to programmatically fetch images without needing further logins. This method adheres to Instagram's API guidelines while allowing automated access to the account's media.