I am new to the Apple world (ecosystem). For me, it started when I purchased an Ipad for my wife which she didn't want after about week. During that time she had setup an Apple ID (yahoo email) along with using the same logon with Itunes. She of course backed up her apps and contacts on Icloud under that ID.
I then decided that I wanted an Ipad and purchased one, so before I started the new Ipad out of the box I decided to change her Apple ID (email address) to one of mine. I wanted to keep the apps, since we did purchase one of the apps on the Ipad, the other apps were free. Well when I started the Ipad for the first time using the changed Apple ID, it wanted to refer back to her old email address when I logged into Icloud. The apps would not load onto the Ipad unless I used her old email address. So I had to go back into manage Apple ID's and change it back to her email address. After all the apps loaded onto the new Ipad I went back into manage Apple ID site and changed the ID to my email address again and deleted the IPad Icloud account and logged into the Ipad (Icloud/Itunes) with my email address Apple ID. Confusing to say the least!
Next, my wife decided she wanted an Iphone, after we got home I figured she should have an entire New Apple ID and hopefully avoid the chaos I went through. I didn't use her original email credentials to make the Apple ID. I made one with a new email address (gmail). I did so and logged into her phone with her new Apple ID. It automatically put the same apps and contacts on her phone even when I logged into Itunes using her new Apple ID. The phone then started asking for her original (yahoo email) to update apps that where under that old Apple ID.
Just last night, her phone needed one of the apps to be updated. I couldn't because it was an app that was downloaded under her old (yahoo) Apple ID. So I just deleted it since it wasn't a paid app. I figure I can just download it again under her new Apple (gmail (ID).
Apple should make this easier, not harder for especially newbie’s like myself and others using these devices. It should be one common ID to work with ALL services i.e. Apple ID, ICloud, ITunes, etc. If an ID is changed/updated that any service that you log into should also carry that same ID. No app or old logon should be carried after it is updated.
Bill