Need to understand deeply the next concepts:

Analytic Account

Analytic Plan

Analytic Distribution 

Analytic Distribution Models

For example, in one of our instances we can't edit the Financials Account Prefix for a new applicability document as a Purchase Order.

And another doubt I have is that in the Demo instance those prefixes are not related to any financial account.. so I need to understand what is the role of the financial accounts and how they are related to these prefixes.

Any help would be appreciated.