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Every morning, I have to speak in English. Suppose that today is Monday.
Do these two sentences convey the same meaning?
On Friday, I had finished the work.
"Had" is used here because it is past perfect.
I have finished the work.
I.e. the work has been finished without mentioning any timeline.
The difference between present and past perfect is in where your temporal focus is.
"On Friday, I had finished the work" means that for some reason I am talking about the state of things on Friday, and that that state included the fact that I had finished the work.
It does not strictly imply that I finished it on Friday, just that by some time on Friday it was finished. (In most contexts, it would be taken to imply that I finished it on Friday, but not necessarily: "Every day last week I sat down to do a bit more on this job. On Friday, I had finished the work, and so I went out to the pub instead").
"I have finished the work" similarly focuses on the state of affairs now, and says that by now, the work is finished. I might have finished it on today, or any day before, including Friday. The longer ago I finished it, the less likely it is to have relevance to the state of affairs now, and so the less likely I am to use the present perfect; but I still might do so if something causes the fact to be relevant now.
The simple past that other writers have mentioned has a different focus. "I finished it on Friday" is a simple fact, with no focus on the state of affairs either on Friday or today.
There is a difference in the two meanings, which you are hinting at already in your question.
By using the past perfect in "On Friday, I had finished the work", you are saying that the work was completed on that day, and you would imply that the work occurred over a time period. Using the simple past "On Friday, I finished the work" (I feel) conveys essentially this same meaning.
By using the present perfect "I have finished the work", you are saying that the work was completed sometime before now, but without specifying when that happened. An important note (mentioned in the linked reference) on present perfect tense is that you should not use it with specific time words. For instance, it would be improper to say "On Friday, I have finished the work."
Following the KISS principle, don't bother with either had or have. Both sentences would still be perfectly ok.
As to whether the two sentences differ in meaning, OP's post already answers that question correctly anyway.
