Try a Google search for "Objective CAE student's book 2008 Exam Practice" I'm sure you will find some practice tests!

They are pretty much interchangeable, however there are a few subtle differences. Here's a great link that shows the difference between -body and -one. Quick Summary: 1. ‘Someone’ is used if we don’t know the person and there are many people to decide from. The use of ‘somebody’ is when we refer to a person but in a narrow amount of selection. 2. ‘Someone’ sounds personal, exclusive, and formal. ‘Somebody’ sounds vague, informal, and distant. 3. ‘Someone’ is more appropriate for formal writing whereas ‘somebody’ is slang, casual, and unofficial. 4. ‘Someone’ is pleasing and likable; ‘somebody’ lacks engagement and appeals only in limited occasions. 5. Both words have indistinct proper usage; both have minor differences. Link: http://www.differencebetween.net/language/differences-between-someone-and-somebody/

1. Would be like someone saying "If I ever saw you at some time in the future I would greet you." Therefore, it is possible for me to see you in the future and greet you. Similar Example: "If I was walking down the street and I saw you, I would say hello!" 2. Would be like saying "If I had seen you in the past I would have greeted you" (but since I didn't see you, I couldn't have greeted you) It is impossible to go back in time and greet you at that same time and place. Similar Example: "I did not see you at the party but if I had seen you I would have said hello!" Hope this is helpful and easy to understand!