The following questions, as asked above, are well known and documented, and to attempt to answer them one must drift into the realms of unsubstantiated inventions and wild conjecture. But here goes…
Question 8:
Why could Harry only see the Thestrals after seeing Cedric, he had already watched his parents die as a child? And on the homeward journey after seeing Cedric die he couldn’t see them either, they only arrived at the beginning of #5?
You could say that Harry never really saw his parents die, what with James being in the hallway and Lily having her back to him. But this is very flimsy, and ignores the question as regards the end of ‘??? ?.
Perhaps one must understand, or maybe come to terms, with the death they have witnessed to see the Thestrals. This would make more sense overall, seeing as how as a baby Harry thought they were simply pretty lights, and with him being in a seeming state of shock after Cedric’s death. This would be further helped by the fact that Harry only seemed to come to terms with Cedric’s death following his talk with Dumbledore at the beginning of ‘??? ?.
This explanation would change the concept of Thestrals. The seeing of the Thestrals would be a psychological, and not purely physical, process, as the imprint death leaves would be enabling one to see them, not simply the act of seeing a human dying.