This is how most of us in India understand the difference though there may be other views.
She went to prison. (She is a convict)
She has gone to prison. (She is a convict)
She went to the prison. (She is not a convict, perhaps a visitor)
She has gone to the prison. (She is not a convict, perhaps a visitor)
She is in prison. (A general statement about the convict who is undergoing some sentence in some jail)
She is in the prison. (A statement about the convict who is undergoing the sentence in a specific prison known to the speaker and the listener)
The activity of ‘going’ DOES NOT continue in the present perfect. If it does, what is the purpose of the progressive?
You have established and stuck to your version by using ‘detained’ and 'serving’or any other straw which is uncalled for and out of the question or context. And it shows you will go to any extent to prove you are correct.
She went to the prison. (She is not a convict, perhaps a visitor)
She has gone to the prison. (She is not a convict, perhaps a visitor)
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The task was to explain the difference between the two. Is it just that the action refers to the present in the first sentence and past in the second one?