Third conditional: if + past perfect → would have + V3. 'would have come' is correct.

'Severe attack' is the correct collocation for an intense bout of illness.

Indirect speech of yes/no question: 'asked' + if/whether + subject + verb.

'Each of' + plural noun + singular verb. 'Every of' is incorrect. 'Each' stresses individual.

'Who' is the correct relative pronoun for people as subject. 'Which' is for things.

'Till he came' is a complete adverbial clause of time answering 'how long'.

'Bad at' = poor in skill. 'Good at / bad at' is the standard collocation.

'Gentle' = kind and mild. Antonym: 'Rude' = impolite/discourteous.

'Competent' = having ability. Synonym: 'Capable'.

'A Farewell to Arms' (1929) is by Ernest Hemingway.

'Animal Farm' (1945) is by George Orwell — a satirical allegory.

'India Wins Freedom' is the autobiography of Abul Kalam Azad.

'Cattle' refers to a group/herd — Collective Noun.

'Girl' refers to any girl in general — Common Noun.

'White elephant' idiom = costly useless possession that is a burden.