Ways to specify different versions of nodes?
In this case, go with taxonomy terms. That way you can organize content around a taxonomy term, one for each version. You can even tag content that is applicable to multiple versions just by selecting taxonomy terms.

Then, you could create a view that says "give me all of the content related to version X" and you'd be able to see those. Plus if you ever wanted to do more than "just nodes" e.g. other entities or bundle types, you can just add the field to those bundles and go on your merry way. Plus, since taxonomy terms are entities, you can add fields and content to those terms and build pages that surround those terms.