Yes. Which brings me to the question, "Is "yes." a complete sentence? I think so.
Arrived exactly at their cut off time is not correct grammar. It is a sentence fragment.A grammatically correct sentence would be, "They [or "The widgets we needed to complete the oscillating framizam" or whatever] arrived exactly at their cutoff [not cut off] time."
"The armadillo is a poor swimmer." is a complete sentence
It is a complete sentence.
Complete the sentence with "He".
Using the word "then" at the beginning of a sentence is not incorrect. However, it does not make a sentence complete. A complete sentence must have, at a minimum, a subject and a verb. "Then" is neither of those.
I presume, assume, you mean, what is the meaning of a complete sentence? A complete sentence has a noun and a verb. I'm glad that I am no longer studying another language.
Yes. You would only need a period at the end of the sentence in order for it to be a complete simple sentence.
Yes, a semicolon could indeed join an incomplete sentence and a complete sentence.
to cut short
Yes that is a complete sentence
No, a complete sentence needs a subject and verb at least.
It looks like your question got cut off! Could you please provide more context or complete the sentence so I can assist you better?