Unlocking Challenges

[Mo0]

I'm curious what the triggers are for actually unlocking the various challenges. I've completed all but two of the challenges. I'm assuming one of the two I'm missing (still ???) is the FINAL CHALLENGE, but I appear to have skipped over Morningstar 1, since I have Morningstar II completed but don't see the first one. Is there a particular way I'm supposed to have unlocked that, considering I've skipped it?

[Mo0]

And, of course, I manage to solve my own problem. Sorry! :(

Turns out the challenges are tied to the highest level you've earned in a particular stage. I finally got the Level 4 in Retro Relic achievement, and whaddaya know, the missing challenge unlocked!

[Saru]

There are three challenges per stage - I know the third challenge per stage is unlocked by getting to level four. I'm not sure what the criteria is to get the first two; maybe just encounter a certain amount of the bad blocks?