That must have been a pretty tight time window :) Per the releases page at https://github.com/reduxjs/redux/releases?after=v3.0.1 , you can see that 2.0 and 3.0 were only a couple weeks apart, and basically just tightened up the API around hot-swapping the root reducer.

Since then, the most meaningful API change was 3.1.0, which redid the `createStore` signature to allow passing an enhancer as an argument (as opposed to the original more FP-style approach).