Answer: No. 2, 3, 4 and 5 are true.
Explanation:
1. Mantle is not the hottest layer as it is cooler than the cores.
2. The inner core is the most dense and hottest layer with temperatures rising up to 5,500 degree Celsius.
3. Mantle is about 1,400 degree celsius hot making it factually cooler than the outer core but hotter than the crust.
4. It is a fluid layer about 2400 km thick.
5. Being the farthest from the hottest surface (inner core) it is the coolest also atmosphere makes it lesser dense.