Forgive me, but what is the point of adding a row to the table if you only want to hide it? You can hide a row in the view with
QTableView::setRowHidden().
A row is a set of columns. How do you propose to put a set of columns into a single column?
Perhaps you mean a row number? You can use the vertical header that is provided by default, which displays row numbers, or provide your own header values (including an empty string).
I have no idea what you mean here. You can have as many rows as memory will allow. Every cell of every row can have whatever value you would like. Every header for a row (column) can have whatever value you would like.