Fun Riddles

Question: I fasten to walk,
and unfasten to stop.

What am I?

Question: How many letters are in the alphabet?

Question: What has 4 fingers and a thumb, but is not living?

Question: There are 31 horses on a cliff, first they jump into the air, then they come down and stop, then they stand still.

Why do they do this?

Question: What happens when you throw a blue rock into the yellow sea?