Why not just use the latest minor release, 13.13? For security reasons, that is the only minor release of v13 you should be using anyway. I think it is a bit much to hope that people will spend their time for free researching obsolete minor releases.
Any node type accessing an index or table
It looks like "Output" includes more than just the columns with predicates and/or being accessed or returned in other nodes.
Not in my hands. For SELECTs it just lists the columns that are needed. Your example is hard to follow because it appears to be just snippets of a plan, with no example of the query to which it belongs.