Making a certain design and strcuture obligatory for all subdomain-blogs

I run the root-blog:

https://1a-spielwiese.de/

and it’s subdomain-blogs:

https://kampfsportlerinnenneuwied.1a-spielwiese.de/

and

https://balletttaenzerinnenkrzbg36.1a-spielwiese.de/.

It should become much more subdomain-blogs.

• If I made no mistakes, both subdomain-blogs have precisely the same structure and design (pages / header-menu, Sidebar-Widgets, Footer-Widgets; Reddle-theme-modifications).
• The root-blog has a slightly different structure (other pages / other header-menu, different Sidebar), but the same Footer and the same Reddle-theme-modification.

I would like, that, when in future time further subdomain-blogs are created,

• they have automatically (and precisely) the same structure and design (pages / header-menu, Sidebar-Widgets, Footer-Widgets; Reddle-theme-modifications) as the already existing subdomain-bogs. (The root-blog should still have it’s sligthly different structure.)
• the subdomain-blog-administrators can only write new blog-constributions and change the content of the already existing pages,
• but can’t creating new pages oder deleting existing pages or changing the names of the pages; as well can’t changing the Sidebar/Footer/Widgets and theme.
• Corresponding I would like to reduce the administration panel for the subdomain-blog-administrator. It should persist only ‘Contributions’, ‘Media’, ‘All Pages’, Comments, and Tools). (But the root-blog-administration-panel should still have the normal appearance/extent. )

(How) is this possible?