As the case with the previous two levels, the Runner is the only available character when first playing through the level. However, after unlocking other characters, any one of them can be used to play Level 3.
Level 3, like the previous two levels, is still very easy. However, it introduces Crumbling tiles, which break and fall when stepped on. However, there are enough normal tiles in the level that it is easy to avoid most of the Crumbling tiles.
However, if a Crumbling tile starts to fall under the character's feet, simply walk or jump off the tile onto a nearby normal tile and continue through the level.