For legal requirements we need to archive each variation of a page that will be served. Is there a way - via query string or a cookie or request headers - to request a specific variation of an A/B or Multivariate test?
The information of which variation a particular visitor got should be stored in the Interactions Collection of your Analytics Mongo DB. You can look at a particular Interaction and look at the Pages element in the interaction. There is a lot of information in there that you should be able to see.
Once you find that information in your Mongo DB, then you should be able to access the Contact Card for a particular visitor, and from that contact card you should be able to get the Sitecore Item ID of the particular variation that was displayed.