From what I know, the column names would only show up when you have a non-dynamic Spreadsheet/Sheet ID as an input.
Let’s say you choose “Spreadsheet 1” and “Sheet 1” as your inputs, then Integromat knows exactly what to look at, and show the column names for you.
If you try to make it dynamic like this one, I don’t think they return the names. Is that a big problem for you?
I’m not sure I understand your second question. Do you mean when you manually input something it works?