Foreign App in Subfolder / SSO Solution

I am fairly new to it, but learning and using CI 3.1.9 in a LAMP test environment and making some progress with MVC and the such. Great framework to say the least!
Two questions arise while concepting my solution:

1. Is it possible to host a "foreign app" in a subfolder within a CI installation on a server? Would that be considered a "static page" by CI? Would I have to control this in the /application/config/routes.php or rather in a .htaccess or both? By "foreign app" I mean something like a simple DOKUWIKI (https://www.dokuwiki.org/dokuwiki) or more complex RESOURCESPACE (https://www.resourcespace.com/knowledge-...l_overview) application.
   
2. If (1) works, would it be possible to control access to such subfolders with a SSO solution within CI such as SimpleSAML or any other user / permission based system?
   

Any ideas or experiences? Thank you very much in advance CI community!