First past perfect and pluperfect refer to the same tense. They are synonyms. Look up pluperfect in any dictionary to verify this. Here at onelook dictionary are more than two dozen dictionaries to get you started.
Second, please see this answer to When is the past perfect exactly needed? It does a terrific job of stating when the past perfect (or pluperfect--they mean the same thing) is necessary.
In general your sentence 1B is grammatical, but it represents rather an incomplete thought. And it is not necessary to use the past perfect/pluperfect tense here. The present perfect or simple past would both be better choices, because they would not represent incomplete thoughts.
Your 1C adds more information to the response but still either the present perfect or simple past would be more common. You don't need the past perfect/pluperfect there because it is clear from logic which past action happened first, namely that you called him first.
In 2B, there is no reason for using the past perfect/pluperfect tense. The simple past is fine. You mention only one past action. And in fact both uses of the verb order refer to that same past action. It would seem strange to think that one occurrence of the same past action can come before another occurrence of the same!
The first sentence of 2C is grammatical But by itself gives an incomplete thought. There is only one past action mentioned, and it occurs two days back. Thus the simple past is better here because you are talking about one action completed in the past. Having us wait until the second sentence to hear the most recent past action (Yesterday when I opened the box) makes it awkward.
The second sentence of 2C is the only sentence in which the past tense/pluperfect tense is used in a way that is intended. You have two actions and you place one of them before the first one. This is pleasant sounding and appropriate.
For example sentences and a much better explanation, see the answer I link to above. And thanks for asking such a good question.
Best Answer
This is a common misunderstanding. Your sentence mentions an action. That action seems to be in the past. The statement uses the present tense. Why?
Some verbs express action. Other verbs express state of being*. The verb "to have" expresses a state of being.
1) I saw the film.
2) I have seen the film.
3) I had seen the film.
In 1), the only verb is a past-tense action verb.
in 2), there are two verb words which form a single verb phrase. The "have" is a present-tense state-of-being verb. The "seen" is a verb without any tense but with the perfect aspect. This form does not express the action of the verb "to see". It expresses the result of that action.
I have seen the film. I possess a result of the action.
In 3), the "had" is a past-tense state-of-being verb.
The structure of 3) is rarely used on its own. Often, it's used to suggest that one thing is even further in the past than another:
4) I had seen the film when I read the book.
The action of "to read" is in the past. At the time of the action of "to read", my state of being included the result of the action of "to see". This suggests that that action of "to see" happened before the action of "to read".
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* As far as I can tell, we use the phrase "state of being" because the word "condition" would be confusing. Verbs like "to be" and "to have" express a condition in the sense of "the way things are", rather than the sense of "something required for something else". We use the word "condition" in the second sense when discussing subordinate clauses, so we use "state of being" when discussing what a verb can express.