I'm new to private tracker. I want to know more details about PassKey embedded in Private tracker torrent file.

1. Can I share the torrent file (thereby passkey)?
I understand that by going so the download is counted in my account.
But will it cause any other problem.
1.1 Does that mean that upload counts as well?

2. What happens if there are multiple users (thereby passkey) in same IP? say same campus or public network.

3. What happens if someone shares .torrent file publicly?

4. What if 'A' shares 111.torrent file to 'B'. B is down/uploading 111.torrent. On top of that he is down/uploading 222.torrent.
[That's two passkey in same Computer]
What happens then?

5. In it possible to change my passkey?
This may be the case when I feel my Passkey is compromised.