How Far Does The Tripcode System Go?

I am curious about how far the tripcode system works. I have a few dumb questions to ask which will help me understand how to give feedback on the system.

First off, are username/password combos unique? From my limited reading on the system, it appears that the same tripcode username can be used by anyone, provided they use different passwords. Is this true, or are tripcode usernames unique? I have no preference either way as identical usernames can be differentiated by the hash afterwards, but both solutions have pros and cons.

Second, is there any level of persistence with tripcodes? It appears that tripcodes are just a string of text that you put on a post to "mark" it as yours. Is there any level of persistence with tripcodes that would allow for account like features such as saving posts or notifications for replies?

Lastly, are tripcodes a permanent combo of name and password? It seems so far that if I were to forget a password for a tripcode, I would just regenerate a new one with the same username and a different password/hash at the end. Is that the case, or is it possible to change your password if forgotten rather than reset the code?

Finally, I am curious about identifiers without a tripcode. I read that there is a conversation identifier that differentiates anonymous posters in threads that have multiple anonymous replies. However, when looking at threads with many replies, I have been unable to find any way to differentiate them. I also am curious if the identifier changes between post replies, website sessions, or browser cookie resets.

Sorry again for the flood of suggestions/questions, but I am think this is an awesome website so far and I am excited to see where it goes. I will create a tripcode tomorrow to test it out and see how the system works in more detail.