What literature should I read to get better understanding of how the Internet works? I want to chase a career as a web developer but I feel as if I don't have the full understanding of how the Internet works. What should I read to fully understand back-end programming?

The standard introductory text is http://www.pearsonhighered.com/educator/product/Computer-Networks-5E/9780132126953.page.  While book learning is fun, you really need to roll up your sleeves to work out what is happening.  There is too much to learn at once, it is better to learn in parallel. Download https://www.wireshark.org/.  Make some connections from your PC and try to understand what is going on.  Ask questions.  Hang out in the forums.  's RFC based answer is correct, but will probably numb your brain if you don't already have a foundation of knowledge.  The RFCs are the ultimate resource, and The Law.  When in doubt, they are the final arbiter of argument.  However, they may not be the best place to start. I have found that only the pain of experience seals my knowledge.  Perhaps you have a more fortunate learning style.

For questions 1 & 2, I suggest for a start: https://www.ietf.org/rfc/rfc791.txt https://tools.ietf.org/html/rfc793 https://tools.ietf.org/html/rfc1035 http://tools.ietf.org/html/rfc7230 http://tools.ietf.org/html/rfc7231 https://tools.ietf.org/html/rfc4271 https://tools.ietf.org/html/rfc5340 https://tools.ietf.org/html/rfc2328