Answer:
I am the noise Santa's reindeers make
I'm written with two letters, said with one and seen with two. What am I?
I cannot be burned in fire or drowned in water
I walk on 4 legs in the morning, 2 legs at noon, and 3 legs at night. What am I?
Forward I am heavy backward I am not. What am I?
What bird can lift the heaviest weight?