It was an additional act of revenge.
The correct answer is "her". This is because an antecedent basically means to whom does the pronoun refer and the pronoun has to refer to Miss Kensington. This is why the correct form is her.
The answer is "Ella spent more time studying than Talia"
The last one "he makes a wish of eternal youth without considering the consequences of his actions" is ended with a question mark but it isn't phrased as a question and should be ended by a period instead. The fourth sentence is the correct answer.