Will I violate copyright if I use elements of a painting (part of an illustration) by a popular contemporary artist?

Question

Design

ps edits and improvements have been made to these borrowed details (parts of the illustration).

Answer 1

If you had indicated the scope of the picture element and the jurisdiction, the answer would have been more accurate.
But, if no other license is specified, your jurisdiction is Russian, and the author lives in a country that has signed at least the Berne Convention, you will violate, at a minimum, paragraphs. 1 and 4, paragraph 2 of Art. 1255, Art. 1256, Art. 1266 of the Civil Code of the Russian Federation, even if the author is indicated.

Answer 2

let's say it's a poster that will be used for a commercial purpose.

Answer 3

Yes, break it, and even more when making edits.
1. Use of a work without the consent of the copyright holder. 2. CC RF
Article 1266
tn museum law.