She is not only beautiful, but also smart --- not ok because of the comma whim is not required when a fanboys connects just two items.
She is not only beautiful but also smart --- Not only adjective but also adjective -- correct
She is not only beautiful, but she is also smart -- not only adjective but she is also --- not parallel.
Q2
Not only she is smart, but also beautiful-- not only noun but also adjective is not ok
Not only she is smart but also beautiful -- same as in A
Not only she is smart, but she is also beautiful --not only noun but she is also is not ok.
Not only she is smart, she is also beautiful --- Not only she --- she is also -- in fact this construction is a comma splice.
which is/are correct?
Is idiom " not only...but also " always to be considered? -- not necessarily.
P.S: A small idea. When you need help with some query, just mention one or two specific names. A wholesale request like yours may prompt none to respond. For grasping such basic doubts, please practice GMAT club's basic grammar book well. Good Luck