How to update the application installed using the old apple id (more in the question)?

Question

iOS

The iphone is signed in with a new apple id.
But it has an app installed using the old apple id.
1. Will there be a notification in the app store (for example, an icon on the app store icon) that an application that is installed using the old apple id can be updated?
2. To update an application that is installed using the old apple id, will you only need to enter the password for the old apple id, or will you need to enter both the apple id and the password for it?