There are only minor changes to parts 0-4. Part 5d, end to end -testing
using the Cypress.io- library is almost completely new material. Using custom hooks has been moved from part 5 to part 7 with some new content.
Part 6, which is about Redux, concentrates on the new, hook-based, redux api. The material on react-router in part 7 has also been updated to use the hook-api. Semantic UI React has been replaced with the MaterialUI library due to lack of maintenance.
Part 8 on GraphQL has major updates especially on Apollo Client, which finally has stable hook based apis. Part 9 on TypeScript is completely new.
Last year's course material can be found from https://fullstackopen-2019.github.io/