(i) In the accident one of my arms broke and my legs bruised.
(Parallelism: which means their should be same form of verb before and after "And". Moreover, this sentence should be in active not in passive because we always write "I broke my arm etc.")

ii)The people who had been raising slogans against the government for many hours they wanted an increase in their salaries.
(Before "increase" we add "an")

(iii) You have been working very hard for the last two years hasn't it?
(It is problem of question tag. We use same auxiliary verb in tag. But remember in perfect and perfect continuous tags we use same tags "Hasn't it" instead of "Hasn't it bee".)

(iv) John could hardly do better than to have caught a bass of such dimension.
("Not" will not be used here as the idea has been expressed by "Hardly")

(v) I, who have no chance to meet him, would rather go with you instead of sitting at home.

(Here is the problem of punctuation as non restrictive clause has been placed after "I". So, we would add commas before "who" and after "him")

(vi) He comes there not only for swimming but also for coaching new swimmers.

(Same problem of parallelism. There should be same form of verb after "not only" and "but also". So, we need to place "not only" with for swimming as it becomes same as "but also".)

(vii) Last time, when he visited the fair, he bought not less than twenty school bags.

(Last time is an adverb of time so it is place in the beginning)

(viii) Ten cattle were grazing in the field.

("Cattle" is a plural word without "s")

Regards,