will Wordpress be aware that it is called via HTTPS and change all links on the pages to HTTPS ?
While WordPress knows if a request comes via HTTPS, it doesn't change all the links automatically. Only certain links are updated to use
https:// that too, without any subdomain part. Any hardcoded links would remain the same.
how i can i force certain pages to be automatically redirected to their HTTPS equivalent permalink (and then back again to HTTP) ?
Short answer: Use this plugin... http://wordpress.org/plugins/wordpress-https/ that has plenty of options.
Bit longer answer: It depends on your exact requirement. For example, if you'd like to use SSL for all WordPress backend operations, then it can be done without a plugin. If you'd like your backend to use SSL and a sub-domain, then the above plugin may help. Still, you may not achieve this with a single WordPress installation. So, sub-domain would probably require its own WordPress installation and a separate database, with regular syncing of common files / folders.
I hope that helps!