Illustrator 2020 vs 2021

[#1]

I purchased Classroom in a Book for Adobe Illustrator 2020 Release then purchased Adobe Illustrator. I ended up with the 2021 release of the software.  Is there much of a difference between the two releases or will I still be able to use the 2020 release book with the 2021 software version?

[#2]

I purchased Classroom in a Book for Adobe Illustrator 2020 Release then purchased Adobe Illustrator. I ended up with the 2021 release of the software.  Is there much of a difference between the two releases or will I still be able to use the 2020 release book with the 2021 software version?

[#3]

Yes.

You can always check the what's new info to add what is covered in the book.

https://helpx.adobe.com/illustrator/using/whats-new.html