About your 2nd question, even I am curious to know what system will consider. Mostly, AR/AP rule is set in elimination, so never tested more than 1 eliminations in US elimination.
A unique requirement when dealing with inter-unit elimination entries is that they should only be reflected in any given group if both the entity and the partner entity which it was doing business with are part of the group. In order to address this requirement US Eliminations uses the concept known as “posting at first common parent”.