title: Bootstrap : As a beginner, which bootstrap version should one learn and use?
body: <p>While trying Bootstrap I found that some classes in v3 and v4 are not the same.
  For example, for a specific thing(in some cases) the class name in v3 and v4 are different. 
  <strong>The main reason for the confusion to choose between v3 and v4 is that most tutorials teach v3 but I'm worried that v4 would replace v3(idk, just an assumption that new things replaces old) and v3 code wont work with v4!</strong>
  Thank you for checking out my noobish question, I'd really appreciate it :)   </p>