How to upgrade CodeIgniter from version 4.1.3 to 4.1.4

That might explain why its not updating framework using composer; also it implies you didn't set up codeigniter  in xampp with composer either ?

have you got a "tree" command with windows to show directory structure ? I'm guessing you have a system directory  ,at the same level as the  app directory?

if i was on linux in your position ,  i think (maybe)  get  https://github.com/codeigniter4/CodeIgni...tag/v4.1.3 
replace system directory , then create patches from my codebase of existing  files  in app, public , writable with the new equivalent  files from 4.1.3 download, in the directories app, public, writable so as to retain your old code, but have it in  updated file , if that makes sense

You are right, the framework was not installed by composer.
I installed it by unzipping the zip downloaded from the website.

i.e basically a manual upgrade

That's what I thought, I'll have to manually update version by version.