You did’t mention FreeCodeCamp. I think that FreeCodeCamp is one of the best places to learn to code. Udemy is nice, but many courses are not that great if you really want to learn to code.
Designing with Sketch and prototyping tools like Flinto or Principle has some advantages. It helps you to create an interactive mockup from scratch in minutes. This is very useful and helps you to move forward quickly during the design process with the customer. Coding still takes more time.