I have, at last, collected all the hearts for this world and can answer questions about it.

This was the least fun one so far; it's short on puzzle solving, and very heavy on frustrating platform jumping. I still have a tip or two that may help you.

Rock Suit Mission:
Forget the rhyme for this one, but it's where you go underground and there's a bunch of rock suit powerups, with the heart behind a wall of ice. Two of the powerups will help you, on the second level. The third one is a decoy and does nothing for you.

100's All That Matters:
Tricky to find a hundred of them in this world. The ones that took me longest to discover were: go to the temple where you have to pick up and throw the snowballs. Instead of jumping up the platforms, go to the far side of the floor on the ground level. The other good place is outside; circle around the back of the temple along a tiny ledge for a whole bunch more (there's a free guy there, too!).

I noticed the extra life I mentioned above, behind the igloo, doesn't get a mention in the FAQ. I've asked Wishingtikal to add it.

what about the heart where you jump across the moving pads.

There's very little advice to give you here except to keep trying! Timing is obviously essential. There's no shortcut or easy method to obtain this heart that I'm aware of. It's probabably the most difficult heart in the game to reach, in my opinion.