I've already removed the "#" from "#LoadModule rewrite_module modules/mod_rewrite.so" in httpd.conf, but still "The requested URL was not found on this server"
Very strange path, that is not the Xampp DocumentRoot. You cannot put folders and files anywhere on your disk and hope that Apache will find it somehow.
XAMPP control panel is in "C:\xampp\", but todolist_demo file was in "C:\UdemyLesson\phpPractice\htdocs", so I moved the todolist_demo file to "C:\xampp\htdocs" and then the problem is solved.