Anyone can become a blockchain node provider in the Bitcoin network. All you need to do is to download and install software from the official Bitcoin website. Besides free public nodes, the Bitcoin network has BTC nodes which are not available to everyone. These are cryptocurrency nodes that are employed by exchanges, digital currency exchange services, wallet sites and other infrastructure projects.
Additionally, the Bitcoin network contains....
In regards to the bolded above, my response to that is if it's not available to everyone then it's absolutely not part of the Bitcoin Network. They are just things that depend on Bitcoin Network to survive. And Bitcoin can survive without them.
So special care must be taken not to merge them with the Bitcoin Network unless they are according to the Bitcoin principles.