I played throug this and I can’t find this prize with yellow symbol and question mark. It was named new player profile or something like that. What was that and were can I have (find) it? Or it is joke? Tell me about it.
It is a new avatar:
In the main screen, click your existing avatar (upper left), to see your options and change it if desired.
Congratulations on finishing!
The prize was the profile pic of a snowman.
You can find it by touching on your hero profile and changing the pic. Those that don’t complete the quest don’t have it.