Your question should be something like: Do they mean the same? Do the sentences "Hello, how are you?" and "Hello, how are you doing?" have the same meaning? And the answer is, yes, they do have the same meaning. 'How are you?' is neutral, and can be used in any situation, in either casual or formal contexts. 'How are you doing?' can be a question about somebody's health, or it can be part of a general greeting in an informal situation.

They are pretty much the same. They are usually just a friendly greeting. They do not usually communicate information. The answer to "Hello, how are you?" is almost always "Fine, thank you, how are you?" or some variation on that. The answer to "Hello, how are you doing" would be "Very well." "Fine" or "Great" would be completely acceptable but "Very well" would be slightly more grammatical. The next sentence in the conversation would probably be about the weather. It's a ritual.

They are nearly the same. Hello, how are you? = how is your health? Hello, how are you doing? = how is your health? OR how is your progress with the task you are doing now?

Yes the same meaning.