Is there a reward for the challenge?

[Naoto]

I completed the challenge but then the screen froze and nothing happened and I had to close it. Was there anything that would happen?

 

[nintendogamer 192]

I completed the challenge but then the screen froze and nothing happened and I had to close it. Was there anything that would happen?

You should have waited, it sometimes does this, but after a while unfreezes and either gives you galasilver (125), Galacredit (no idea how much, I've won 0.02$ once) or a key that is then in your library under G.Giveaways. It can also show an error, where you're out of luck.