It’s a little hard to say as we don’t follow the usual curriculum, but as an example - after completing 2 levels of the old Spanish course, one learner went on holiday to Spain and spoke just Spanish while she was there. She managed extremely well. Her progress is recorded here: How it started and how it’s going
The ‘Skip’ functionality doesn’t take belts into account, but sometimes it does take you past a belt threshold. To go back, just click ‘Revisit’ a few times and you’ll get more practice of earlier material.