What was Sauron?

[obloquy]

1. Orcs were originally elves, captured and corrupted by Melkor. Whatever may happen to their spirit after death is another discussion (and a difficult one, feel free to start it as a new topic).

This is not wholly accurate. Granted, it is presented as a fact believed by the Elves in some of Tolkien's writings. However, his latest ideas on the origin of Orks deny this concept. Here's a succinct little snippet from Morgoth's Ring:

On the typescript of AAm my father noted against the account of the origin of the Orcs: 'Alter this. Orcs are not Elvish'(p. 80).

MR contains some extensive essays on Orks that I'm sure you would be interested in.