Hi,

I wanna know something about the following two. Where, When and Why they are used? and In which English?

1. How are you?

2. How are you doing?
Both say basically the same thing to me.
1. How are you?

2. How are you doing?

Both are commonly used as a greeting, as a general inquiry about the other person's health or state of affairs, but #2 is also often used to inquire about the state of a particular project, effort, etc.
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Hi,

To me, with a British background, 'How are you doing?' as a greeting is more informal.

Clive
Please do not use abbreviations such as "how r u" in this forum. Also, "wanna" is heard in conversation but you should never use it in writing (if you want to be taken seriously).

(From your photo, you look like a man who wants to be taken seriously!)