According to MGMAT SC,
The word before and after indicate the sequence of events clearly and emphatically enough to make the use of Past Perfect unnecessary.
eg. RIGHT: Laura LOCKED the deadbolt before she LEFT for work.
However, According to Aristotle SC,
RIGHT: Before John won the lottery, he had been a poor locksmith.
WRONG: Before John won the lottery, he was a poor locksmith.
also,
RIGHT: John had traveled to many different countries before he decided to settle down in New Zealand
I am now confused. What is the right usage? Should I use past perfect/past perfect continuous OR simple past when the sentence already has an emphatic preposition, such as before, indicating time previous to another past event?
Can anybody please help me understand?