I am preparing an odt file and I want to give it someone else.
How can I protect it from changing just its style?
I mean, someone else can copy/past her content into the doc but she should not be able to change the doc’s format/font/size/color … 
!!!
Thank you:)
You can’t do that, however you can mitigate the adverse effects of changes.
First, give strict instructions to the external contributor: only text entry is allowed. Paragraphs can be formatted by styles (this may be necessary, e.g. making headings or quotations). Words may be highlighted with character styles.
Warn your contributor that any direct formatting (use of toolbar buttons or keyboard equivalents for bold, italics, center alignment, etc.) will be wiped out on return. This is intended to force use of styles. Tell also that any new style will be deleted (any addition should be discussed between you to maintain consistency).
On your side, base your document on a template where all your styles are defined. I suggest you enter some fixed text in the template, for instance the date of latest update (use literal text, not a field). Don’t send the template to the contributor, only the document to review/edit.
When you receive the contribution, change the fixed text in the template (the literal date or id) and save the template. Then open the contributed document. Since the template is newer than when document was typed, Writer asks if styles in documents should be updated to template state. Answer “yes” to revert the styles to your configuration. To remove direct formatting, Ctrl+A and Ctrl+M (clear direct formatting).
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Thanks for your attention and specially for your answer :). It’s unfortunate. In Microsoft Office Word we can do it by restrict editing in developer tab and I thought It will be able in Writer too. Anyway thank you for your answer. It seems to be very helpful 
In addition I am new in writer and here.