We can access current privilege policies from https://stackoverflow.com/help/privileges. However, changes to the policies are not documented there. There has been at least one notable change - the requirement to access review queues was increased from 125 to 500 reputation. How can historical data on privileges be accessed?
Internet Archive to the rescue!
- For 2008-09-16 to 2010-11-10, refer to /faq.
- For 2010-11-11 to 2013-06-30, refer to /privileges.
- For 2013-07-01 to (present), refer to /help/privileges.
(Note that "access review queues" wasn't a concrete privilege for a long time, and /review doesn't give much indication when you're not logged in (the Archive-bot isn't) - you'll need to find those elsewhere, e.g. on Meta.)