If you are new to Azure cloud computing, then the best way to learn is by going through the Microsoft Azure fundamentals course. Very well crafted course for beginners.
The following URL is the cheat sheet for calculating the numbers of ip address from a CIDR range.
NodeJS should not be installed using sudo / root. The following link has the details for correct nodejs installation
Here is a quick start up article to unit test node.js application using frameworks like Mocha, Chai, Sinon.
The following blog post can be referred for CI/CD setup using Minikube, Helm, JenkinsX