how to preserve formatting across save and reopen

using version:
Some of the following may be old, it was true the last time I wrote here.
Build ID: d3bf12ecb743fc0d20e0be0c58ca359301eb705f
CPU Threads: 2; OS Version: Windows 6.1; UI Render: default;
(OK Win 7 is what I think I have)
Locale: en-US (en_US)
I have a short story I am submitting to a magazine. The magazine uses this format:
Note that the first page does not have a page number or headder and the rest of the pages do. And that the first few lines are single spaced and the rest double.

I can get the document to be that way. Then I save it, close it, reopen it, and much of that is gone.
It is in the wrong format for magazine submittal

You don’t tell which is the format you use to save your document. If that’s not LO native format (ODF), then it may happen that round-trip is not prefect, and also it may be that you need to change your formatting a little. E.g., you may specify different first page format in several different ways: you may define different header for first page in the style; or you may define different styles and define their sequence; or you may insert page break with style. They may have different support on round-trip.