Are these all not one and the same? It's an Apple account, a single Apple account, that's used to access all their services, isn't it?
The last time I had to deal with this an Apple account was much like a Google Account or Microsoft Account in that there was one userid (typically a master e-mail address) and password that's used to access all services.
Brian - Windows 10 Pro, 64-Bit, Version 2004, Build 19041
Always remember that computers are just glorified light bulbs - they rarely fail in continuous use and usually go pop when turned off and on.
~ Technician with the username Computer Bloke, on Technibble.com