Сделать 3 и желательно 4 много

'i was used to doing' и 'i used to do' - это разные предложения по смыслу и по грамматике.

выражение 'to be/get used to doing something' означает "привыкнуть/иметь привычку делать что-то". например, my mom is used to getting up early in the morning. = моя мама привыкла (имеет привычку) рано вставать.

выражение 'used to do something' используется, чтобы рассказать о старых привычках, т.е. о том, что раньше регулярно происходило, а теперь нет (повторяющиеся действия в прошлом). переводится 'used to' - "", "имел(а) " например, 'i used to play with dolls' = раньше я играла в куклы (а теперь я уже большая и в куклы не играю).

таким образом, предложение 'i was used to doing' означает "я имел (когда-то в прошлом) привычку делать что-то", а 'i used to do'= "раньше я делал это, а теперь нет (причем, это не было привычкой, а просто происходило регулярно в прошлом)"

1. by two o'clock the teacher have examined all the students. 2. on my way to school i remembered that i had left my report at home. 3. all my friends were glad to hear that i had passed all the examinations successfully. 4. poor oliver was laying unconscious on the spot where sikes had left him. 5. he opened his eyes, looked around and tried to remember what had happened to him. 6. all the passengers have seen at once that the old man travels a great deal in his life. 7. by the time we came to see him, he had returned home. 8. during the holidays my friend visited the village where he had been living in his childhood. 9. when they entered the hall, the performance already had begun. 10. when came home, my mother told that she had received a letter from grandfather. 11. where you was working/worked before you entered the institute? 12. he studied рмbefore he entered the university. 13. lanny said that he had gotten his education in cape town. 14. the boy wanted to act the main part in the play because he had organized the theatre. 15. lanny doesn’t know who attacked him in the darkness/lanny didn’t know who had attacked him in the darkness.16. the girl was glad that she had found a seat near the win dow. 17. suddenly he remembered that he hadn’t rung her up in the morning. 18. by the time the train have reached the city, he had made friends with many passengers. 19. when my uncle left, he hurried to the station to book a ticket. 20. she thought that gert and lanny had quarreled/she thinks that gert and lanny quarreled.

насчет 6 не уверена, что правильно.