For this you have to complete all objectives in each level. Thats collecting all balloons, the star, not dying, the ring of fire and finishing on time. Not losing a life will be your biggest problem.
know each level and keep practicing them until you know the best route to take to get everything on time, dont worry about dying just concentrate on the other objectives until you can finish in time with minimal deaths.
When your comfortable with the level layout, play the 4th bonus level and collect the secret item to the left of the map, finish the level. You will now have 9 protections, giving you 9 mistakes before losing a life. If you use up your protections just replay the bonus stage for a new set and start again.
To unlock the bonus level you just have to rank up, cant remember what rank you get it at, I was rank Awesome when I finished, second last rank. To rank up you'll have to finish off some of the objectives in levels that you may have missed, balloons, stars, not dying etc. I had all objectives except some of the bonus level ones
The 4th bonus stage will appear before the 18th level and the secret item is a picture of a dragon, it can be a pain to get at first but after a few tries it should be no problem