by pgm123
Here's a thread on 3rd vs 4th: https://boardgamegeek.com/thread/2275245/3rd-vs-4th-printing...You can also check out this site for the latest rules: http://root.livingrules.io/
You can play any version of the game, even the first, and be completely fine. They're tweaks to the balance and clarifications of rules. Even the major changes are not necessary to enjoy Root.