Unfortunately, no. It is even worse than you think. In Writer, odd pages are hard-wired to right-hand page and even pages to left-hand side. This is particularly troublesome for RTL languages like Hebrew and Arabic.
One could imagine to “declare” the document single-sided (where page parity does not matter at all) but this is impossible presently.
Yes and no.
There is no built-in function for it. A possible workaround in simplest cases, i.e. some unnumbered front material followed by a single sequence of numbered pages, is to put a reference after the last word and to cross-reference its page number. If you have front+main discourse+annexes with a different numbering, you separate the size of the main topic and the size of the annexes using the same technique twice.
Issues with your template
Cover page
Your cover layout is bound to fail if you modify the page style in the slightest way, e.g. margins or font face.
You vertically spaced your data with empty paragraphs. And you are not consistent: top spacing is Default Paragraph Style, then they are TITRE DU DOCUMENT.
To illustrate this: Garamond font is not installed on my Fedora Linux computer; it is replaced by some serif one. But metrics is not the same and the two lines which are supposed to be at bottom of page one are now at top of page 2.
Vertical spacing is part of the semantic significance of a paragraph style. You should then have your TITRE DU DOCUMENT or built-in Title for middle information and some other “Academic Context” for the bottom lines. You tune spacing through Indents & Spacing Above and Below parameters.
You should never use Default Paragraph Style for any text in your document. Due to the hierarchical organisation of styles, all styles inherit from it. It is very handy to set default custom parameters (such as font face and language) to be shared by all others. Modifying these settings are instantly forwarded to the others (unless they are overridden).
Fortunately, you are not aware of this tree-like structure and inheritance rule and you created your custom styles independent from Default Character style (DFS). Otherwise, the tab stop you added to DFS would have been present everywhere.
Chapters
Instead of using the built-in Heading n collection, you recreated one as TITRE DE CHAPITRE, SECTION/1, SECTION/2, SECTION/3. They are all independent except SECTION/3 which inherit from SECTION/2. This is inconsistent and will cause you problems when you tune your layout.
You added some dummy manual list numbering to your styles. This creates a conflict with Tools>Heading Numbering which can now no longer be used. Don’t do this. In addition, you don’t benefit from automatic numbering. "Chapitre " and " : " (non-breaking space-colon-ordinary space) can be inserted automatically as “separators” around the number.
You have a negative first line indents on your outline levels 2, 3 and 4. They send start of text in the margin. Though you can technically do it, margins are theoretically no-print areas (at least where the main discourse is concerned - you can send notes or graphics into the margins though, provided it remains an exception).
Global relationship between styles
You should try to use built-in styles. They provide a good example of a consistent organisation where styles are logically dependent from some “master” (e.g. all Heading n inherit from Heading; or all "usefulé styles for the main topic inherit from Body Text). This careful hierarchy allows to control formatting from a very small number of “key” styles and avoids pitfalls.
For example, all your heading styles are forced to Garamond but you left CORPS DE TEXTE in Times New Roman. And your DFS is Liberation Serif here. If you kept the factory hierarchy, you only had to configure DFS and Heading for Garamond and all your document would be switched to Garamond without the need to track usage in every style.
Similarly, your recreated page styles but they were not fully configured. Overflow of your PREMIERE PAGE switches to Default Page Style and not to your PAGE PAR DEFAUT.
Reuse of the "template"
A Writer template is a document with .ott extension. It is created with File>Templates>Save as Template and can be edited with File>Templates>Edit Template.
There are many good reasons to use an .ott, among which the main ones:
- there is no risk to overwrite the template when saving because Writer changes the extension to .odt as soon as you create a new document
- when you change your styles in the template, your documents are automatically updated next time you open them
And an advanced one: provided you wrote your text exclusively with styles without any trace of direct formatting, you can dramatically change the layout of the document by assigning another template to it, without caring to change or check anything in text.
This magic is possible is you educate your mind to think about styles as a semantic meta markup where styles (paragraph, character, page and even list) denotes the value or significance of the styled object, not its visual appearance. Appearance is an independent aspect handled in style configuration. You then realise that the most important job for the author is to assign styles. Formatting can be deferred to later time.
