Skipped the challenges for the last 4 levels but still got 3-stars and points.
Trading one inconvenience (2 days worth of challenge-grinding) for another (not being able to select levels 26 through 30 from the selection screen). To get back to these levels, I have to open level 26 and fail it, click to level 27 from the fail screen, etc. To open level 30 takes about 4 minutes.