Looks like we need some clarification here.
In German grammar, pretty much as in English, the term "perfect tense" is a bit misleading in that its original function is to express an action that took place before the present but still somehow lingers around, so to say; see my example with the airplane. In other words, it's not "perfect" in the original sense of the word. I assume that this confusing use of the word "perfect" was caused by the fact that such grammatical terms (perfect, imperfect etc.) originally were mainly used in Latin grammar, where they made perfect sense (pun intended).
As stated in other posts, the German "perfect tense" has been gradually taking over the function of the imperfect tense, which, in German, isn't really "imperfect" but just a preterite ( Präteritum ). That's the main reason why I would never use the perfect tense for something that entirely happened in the past. So, my answer to your first question is "No," although I'm fully aware that I'm belonging to a decreasing minority. " Der erste Weltkrieg hat nach dem Attentat von Sarajewo begonnen " kind of implies that WW I is still raging.
I used the example " Ich konnte den Zug gerade noch erreichen " ("I was just able to catch the train") to demonstrate that the imperfect (!) " konnte " per se doesn't imply any repetitive or other grammatical aspect, because there is no such thing in German grammar. " Konnte " means it happened in the past, no matter if that was many times, over a long period of time, only once or whatever. In my example, there was only one train I had to catch, time was tight but I made it. No repetition, continuation etc..
I'm not quite sure what your second question means, but "I have been able to catch the train" would translate as "Ich habe den Zug gerade noch erreichen können," which (see above) kind of implies that I'm still on that train, both in English and in German but not necessarily in somewhat low-level colloquial southern German.
I'm not quite sure about the meaning of your last sentence. Could it be that you misconstrued the meaning of the word "period"? I used it in the (mainly American) sense of what Britons would call a "full stop," as in "a punctuation mark that ends a sentence." In other words, it means something like "Case closed," making clear that there was not even a hint of the repetition you had mentioned.