You can find PDF versions and exercise previews of Part 2 on educational communities such as First English For All Children on VK.
Searching for "GDZ" (ready-made homework answers) for for the 4th grade, you'll find that these materials are typically part of a larger educational set designed to accompany textbooks by authors like Vereshchagina or Afanasyeva. Resources for Barashkova's 4th Grade Grammar gdz po angliiskomu grammatika barashkova 4 klass chast
Plural forms and the use of articles ( a/an/the ). You can find PDF versions and exercise previews