Getting started with framemaker

Your questions were:

1. How do I remove the total number of pages of content in a 26-page template file? The content can also be removed, leaving a file of up to 10 pages with styles, paragraphs, etc.
2. In that case, can I not find anywhere in an instruction how to insert, say, 10 blank pages (left and right) based on, say, the template described above?

IMHO you show body pages in the screen shot. Hence:

to remove an arbitrary number of successive pages: Put the cursor at the start of the text which you want to remove. Hold SHIFT while you click at the end position to select all what you want to remove. Use the Del key to remove.

Blank pages per so do not exist in FM. You may have several empty paragraphs with the property "start on top of page". This will look like the corresponding number of empty pages.