I have a question regarding forking web/app projects available on Github for making my new project for web and apps. I have read somewhere somebody written on their Github profile that the project has been bootstrapped from https://github.com/facebook/create-react-app.
So if I fork such projects or the other projects available on Github, can I use them for my own work? Will I have complete right over the source code that I will be using?
Quoting the GitHub docs
A fork is a copy of a repository. Forking a repository allows you to freely experiment with changes without affecting the original project.
So, to answer your question, yes you will have control of all your code but if you refer by rights to legal, that might be be different according to the license of the project.
In this case create-react-app comes with a MIT License so you are free to do anything you want.