I've really tried for a while now, or I wouldnt be asking.

I'm in the second system, the one where one is the toxic with the blue healing plants and the other is the volcano style.
But I dont get anywhere in each one, except find some stoopid crystals.

About the game generally:

1. Whats with the crystals, do you need them or are they like "catch them all" bonus things ?
2. Is each planet solvable on its own, or do you have to look for solutions elsewhere sometimes ?
3. Is it possible i missed something, on the first system that i would have needed now,
cause I really tried hard.

Specific:

A: Where do i get the solution for the shoot the arrows riddle on the toxic planet ?
B: What to do on the lava planet ?
C I already got past the laser with the key, and got the tech-thingie but i would really like to know why.
I just went there a second time after a while and then it was suddenly open.
Does it have to do with the crystals ?

Please help, this is driving me bonkers.