2 верно
3 None of the teachers at our school let their students leave early. (Если после none нужно использовать существит., то добавляется предлог of)
4 I have got hardly any Facebook friends.
5 Several people I know are bored with Facebook.
6 They both are very lazy. (в сочетании с местоимениями both ставится после местоимения)
7 Neither of them works.