Questions & Answers about Кравець вкоротив рукав.
Here it is capitalized simply because it is the first word of the sentence.
As a common noun, кравець means tailor and is normally written with a lowercase letter: кравець.
It can also be a surname in real life, since Кравець is a common Ukrainian last name. But in this sentence, if the meaning shown to the learner is the tailor shortened the sleeve, then it is just the noun tailor, capitalized only because it starts the sentence.
Кравець is in the nominative case because it is the subject of the sentence — the person doing the action.
So the structure is:
- Кравець = the tailor, the subject
- вкоротив = shortened
- рукав = the sleeve, the object