1.
The first question is about the tense we should use after "as soon as". In a sentence such as this:
I had left when the phone rang.
you need to use the past perfect in the second clause to show which action came first and which – second. However, when you use “as soon as”, the sequence is clear and it is normally a matter of preference which one to use, so both your examples will be correct. In American English the preference would normally be past simple. The past perfect would emphasize the fact that one action was complete before the other one occurred. (an explanation given in Grammar for Teachers by Andrea DeCapua)
2.
In the second pair of examples they are both correct again. It is unnecessary to use past perfect because the time is mentioned and the sequence of events is clear. Also, the actions are described in the order in which they occurred. You can use the past perfect if you want, to emphasize that one was before the other.
3.
The third question was about the sentence
He said that the moment he first met her, he felt something special and began to keep a diary.
The actual words the man said must have been:
"The moment I first met her, I felt something special and began to keep a diary."
When you report his words and begin with “He said”, the entire phrase shifts one tense back and becomes:
He said that the moment he had first met her, he had felt something special and had begun to keep a diary.
Although this is the grammatically correct sentence, it is very common that the past simple does not become past perfect in indirect speech. When reporting, native speakers tend to make present tenses past ("I am studying" - "She said she was studying") but very often do not care to make the past tenses perfect, as grammar books always teach us we should.
That is what makes both these sentences correct: "He said that the moment he first met her, he felt something special and began to keep a diary." and “He said that the moment he had first met her, he had felt something special and had begun to keep a diary.” (have a look at the end of this page)
The past tense and present perfect tense may seem similar, but they are very different. The past tense describes a specific event, e.g. "John ate an apple". It's like a story.
The present perfect tense on the other hand is not a description of a specific event. It is only an assertion that there exists an event fitting the details of that sentence, and the event completed before the present. "John has eaten an apple" means the event of "John eats an apple" occured at least once in John's lifetime.
If I were to draw a picture that directly represents "John ate an apple", I would draw a picture of a man eating an apple, an the "time within the drawing" would be in the past.
If I were to draw a picture that directly represents "John has eaten an apple", I would draw nothing, because the sentence is just an abstract fact like "Most people use cellphones".
Therefore, if someone asks you,
What did you do for the holidays
You should reply with a description of "what you did for the holidays". You can give a description by using the past tense. You could say:
I went to Switzerland
If you had replied "I have been/gone to Switzerland" it would feel very out of place -as if you were saying a random fact about yourself.
Keep in mind that I these are just my observations as an American English speaker. I've heard that British speakers use the present perfect tense to also describe specific events, but Im not sure.
Best Answer
Had you been is incorrect here. It's the past perfect and it's used when you're talking about something in the past and you want to make reference to something that happened even before. E.g. He told me he had been admitted to hospital.
But you could choose between were or have been, depending on the situation.
If your friend is fine now, you should use were you admitted to hospital or not?, because it's something that if it happened, it has already ended. This is the past tense.
if your friend is still ill and you want to know if he's in hospital or in bed at home, you should ask have you been admitted to hospital or not?, because in case he is in hospital, he would still be there; the action has not ended yet. This tense is the present perfect.