Migrations - very confusing

If you need to roll back, you have to use $this->migration->version(<VERSION>);
So in your case latest version is 2, and you need to go back to 1, you would call $this->migration->version(1);
It will automatically call "down" method from 002_do_step2.php.

I personally prefer "latest()" - that way I don't have to change $config['migration_version'] each time I need to migrate to a newer version.