Unable to install certain apps from the App Store using my iPad mini 4

I have an iPad mini 4, which was set up as myself. I erased all content and set it up with my child’s Apple ID (which she was using on an iPod touch). However now it won’t allow me to install certain apps, such as YouTube, saying I need a newer version of iOS to install it - but I had the app before on the same device so I’m extremely frustrated that it won’t let me get it now when all I’ve done is change the Apple ID associated with the iPad! Please help!

[Re-Titled by Moderator]

Original Title: Unable to install apps