The riddles are different, depending on which level of difficulty you chose at the start.
Warning; SPOILER - below are the answers to all the possible riddles.
Give it air and it will live . Give it water and it will die.
What has a head and tail but no body
What has teeth but can't eat
Riddles for Jr. Detective level:
1) I run all day and never walk, I tell you something, but I do not talk!
What am I? .........Watch or Clock
2) When you look at my face it is easy to see, You're looking at you when you're looking at me!
What am I? ..........Mirror
3) Soft as a petal that falls from a tree, the more I dry the wetter I'll be!
What am I? ..........Spongeor Towel
Riddles for Master Detective level:
1) The more you make the more you leave behind?
What am I?........ Friends (Other answers can be Tracks and Footprints)
2) What is full if holes but holds water?
What am I?........ Sponge
3) What has four fingers and one thumb but is not alive?
What am I?....... Glove