Answer 1

That depends on what you want to make. If you want to develop iOS app you can learn swift.If you want to develop desktop applications you can learn c++,java,c# etc .If you want to make a website you can learn html ,css,javascript, jquery etc. If you are interested and passionate of becoming a coder , you can learn all

Answer 2

The courses here are only tutorials of the basics of every language; even if you did them all, you would have a lot left to learn in every single one.

Better choose a direction and try to become reasonably good in one language (or a smaller set), which involves writing a lot of code yourself for practice.