if you connect from mobile device to http://192.168.1.3/HelloWorld.py on server with CGI then code should be executed on server, not on mobile device. If CGI doesn't work then server may try to send code as normal file and then mobile mdevice ay try to run it locally but it is wrong - CGI server should run code on server.

At start I would put code in subfolder cgi-bin to run it as http://192.168.1.3/cgi-bin/HelloWorld.py because most CGI servers as default run code only in this subfolder.

On Linux script would need shebang

#!/usr/bin/env python

in first line and it should be executable

chmod a+x script.py

CGI has also some rules how to generate data which it will send to client. It may need at start extra information for HTTP protocol - and using only print("Hello World") may generate wrong data and it may have problem to send it. You should have it in any tutorial for CGI scripts. See module cgi

To run Python's code Apache needs module mod_cgi, mod_fcgi or mod_python

mod_cgi and mod_fcgi can run scripts in different languages: Python, Perl, Ruby, etc. and even Bash, PHP or C/C++/Java

Python3 has standard module http which can be used also as simple server

python3 -m http.server --cgi 

and it will serve all files in folder in which you run it. And it runs files from subfolder cgi-bin/ - see doc: http

You can't force mod_wsgi compiled for one Python version to use a different Python installation for a different version. This is because mod_wsgi actually links the Python library for the version it was compiled for, it doesn't just run the python program of some arbitrary version.

The only thing you can do is uninstall mod_wsgi from system packages (which uses Python 3.5) and install mod_wsgi from source code yourself and compile it against Python 3.6.

Also, neither of the paths you gave WSGIPythonHome and WSGIPythonPath were correct anyway. When you install mod_wsgi from source code, don't set those directives as they will continue to screw things up.