There is structural difference between those two sentences.
The first sentence is in past tense.whereas the second one is in past perfect tense.
When it comes to the meaning, the second one is generally used to indicate that the subject left all his friends and peers.In that sentence, all refers to people.
While in the first sentence, he might mean that the subject of the sentence left all his possessions i.e objects.
But, one may interchange the meanings according to one's wish.
I think there is no need to answer your second question, as it is already mentioned in previous answer to this question by P.E.Dant