What is most using programing language?

Answer 1

The languages in the first cluster, Java, C, Python, and C++, are pretty much universal languages. They're not tied to a specific programming platform or focus. The most interesting clue is the second cluster, containing JavaScript, C#, PHP, and Swift. JavaScript and PHP are mainly web development languages.
FOR more:
http://www.zdnet.com/article/which-programming-languages-are-most-popular-and-what-does-that-even-mean/

Answer 2

see the chart here:

https://www.google.co.in/amp/s/stackify.com/popular-programming-languages-2018/amp/

Answer 3

There is no clear answer to that question, depends on the purpose of what you want to do with it :)

Otherwise you could look up statistics from sites like Github to find some reference.
https://www.google.nl/search?q=most%20used%20programming%20language&ie=utf-8&oe=utf-8