You should finish challenge as fast as possible to receive rank. It's 2 hours or less for million challenge, 4h for billion challenge and 6h for trillion challenge.
How do you unlock trillion challenge? I completed billion challenge in 4 hours and it said no rank and didn't unlock trillion challenge. How do I unlock trillion challenge?
It's not letting me unlock trillion challenge, when I finished billion challenge in 4 hours, it said there was no rank, and trillion challenge wasn't unlocked. What am I doing wrong?
 "Hill Climb Racing"){kind=icon}
 "Get A Little Gold"){kind=icon}
 "Bloons TD 5"){kind=icon}
 "Decision 2"){kind=icon}
 "Driving cars"){kind=icon}
You should finish challenge as fast as possible to receive rank. It's 2 hours or less for million challenge, 4h for billion challenge and 6h for trillion challenge.