eitijan wrote:Here, In option C 'whose' is followed by "living, but" and 'whose' being relative pronoun should follow that it is relating to.
Please clear the gap in my understanding.

Look at the logic of what is going on. You have a list, both elements of which modify composer.

First Element Of The List: who receives popular acclaim while living

Second Element Of The List: whose reputation declines

composer who receives popular acclaim

composer whose reputation declines

composer who receives popular acclaim and whose reputation declines

composer who receives popular acclaim but whose reputation declines

Similar situation:

Voters prefer candidates who understand policy and how to make it and who represent the country well.

Joachim Raff and Giacomo Meyerbeer are examples of the kind of composer who receives popular acclaim while living, often goes into decline after death, and never regains popularity again.

This is a parallel structure.
Composer who receives…, often goes…. And never regains….

(A) often goes into decline after death, and never regains popularity again

(B) whose reputation declines after death and never regains its status again
Its is a pronoun that refers to composer which is incorrect

(C) but whose reputation declines after death and never regains its former status


(D) who declines in reputation after death and who never regained popularity again
This is a incorrect parallelism because of verb tense receives, declines and regained.

(E) then has declined in reputation after death and never regained popularity
This is incorrect parallelism