Before going for this achievement, you must unlock
to get access to the challenge cave. You should also fully upgrade all the equipment. You can complete the game since you can return to the world afterwards by loading the game from the same slot.
I found
this post by dieselmanchild extremely helpful although it's written for Playstation and the cloud save manipulation is not directly applicable.
Here's the breakdown of my approach based on his writing.
1. I fully upgraded the backpack (including the relevant Cog Mods) and farmed all 12x5 slots with Blood Rocks in the Leaky Lodge cave next to the Below the Acid Swamp tube in Yarrow.
2. I returned to El Machino and made sure to have the following Cog Mods which proved useful: Return to Sender, Mid-tile Express, Re-Circle of Life, Gordon Reflexes, Cougar Paws, Karma Plates, Vidar Boots, Aramid Armor, True Survivor, Ultra Composite Armor, Molotov Vaccination, Cruise Control, Maverick Afterburner, Air Cooling, Ramjet Vigor, Long-Range Grappler. I also made sure that none of the Fate Engine Cog Mods were enabled.
3. I traveled to the challenge cave entrance: I went right from the town to the Windy plains and then used the jet engine to fly right staying at the top of the level.
4. I didn't care about the order of the trials and started playing them for real without trying them out first. Since the game saved at the beginning of each trial, I kept close track of how how many hearts I've lost. As soon as there were too many, I pressed
to navigate home and quit the game. Once I reloaded the game, I was back at the beginning of the trial with all my health back. I made sure not to lose more than 4 hearts in any of the trials accept for the Trial of Rockets (I lost the extra life from True Survivor here and a couple of hearts on top of that) and the Trial of Escape (I lost 7 hearts here). In between the trials I recovered my lost health by discarding the Blood Rocks thanks to Re-Circle of Life.
The Trial of Skillness deserves a special mention. I found the following video very helpful to learn about the special jump mechanics involving running by pressing
together with
or
. And also to see how to solve individual jumping puzzles:
I had to change the way I hold the controller for this trial. I was only holding it with the left hand as usual. I was pressing the
with my right index finger and tapping
with my right thumb to jump.
It took me around two hours altogether to unlock this achievement.