1. This is the book whose cover is red. This is the book. + Its cover is red.

Question

2. This is the book of which the cover is red. This is the book. + The cover of it is red.
=> This is the book the cover of which is red.
=> This is the book whose cover is red.

( Are they right and grammatical? )

Answer 1

1 is OK.

2 is grammatically correct, but very awkward (phrasing not used).

Better would be to write this: This is the book with the red cover.