What are the special levels and what do you get if you beat them all

[Patch]

And were they in the original version of the game or were only made for this version?

[🌌 LetsPlayNintendoITA 🌀]

they're completely new and Collecting four out of six stones will allow the player to buy the strongest sword and the only gated off item in the remake: the Gallic Sword. Collecting all six stones activates the secret doors in the village.

[chrcoluk]

To further expand on the answer.

In the original game, charms could drop from enemies, and also some chests gave them, they gave you charm points, armour also gave charm points in addition to defence, a lot of shops had items locked behind charm points requirements. So you couldnt e.g. go straight from the default equipment to crystal.

In this version, all the charm point requirements were removed except for the Gallic sword, armour no longer gives you charm points, charms are no longer a standard treasure, and as above they now only used for those things.

The secret level for the mouse was interesting, very challenging, I only discovered one of the secret levels by myself, had to find a guide for the rest, and also needed a guide to figure out how to not break the blocks as lizard man, I did appreciate the extra content.