What's the main difference between testing and debugging when it comes to a computer program?

Does the word "debugging" really signify anything when talking about coding?

Do I have to be an expert in every language's nuances before I start creating code?

Debugging was performed, however the problem persisted. In this situation, what choices do you have?

Why is it necessary to build a program that is used just for debugging in order for the debugger to function properly?

Why are pass-by-value and pass-by-reference constructs required in modern programming languages? Why can't we just choose one of the two possibilities? Please describe the benefits of having both in your answer, as well as the reasons why it would be foolish to have just one or the other.