Hi Gustavo,
1) Yes. The firmware is the only difference between G2 and G3. There was no board re-spin.
2) Unfortunately, you will need to re-run a learning cycle on the battery, since some of the data flash parameters may have changed. GaugeStudio does not have the same ability as bqEasy to create the golden pack information, but you should still be able to use the EVSW and then run bqEasy from there.
Thanks,
Michael