Ocaml

So I've got an Ocaml assignment and I know shit about Ocaml. Wanna help a retard with his homework? I'll probably learn faster if I see examples. So, my tasks include:

1) Write a function that flattens a list of lists
2) Write a function that will count an object's occurences in a list
3) Define a function that will create a list containing a chosen number of duplicates of a certain object
4) Define a function that will square all numbers in a list
5) Write a function that will check if a list is a palindrome
6) Define a function that will return the length of a list
7) Define a function that will append two lists

>>35
so, how do you flatten "HAX MY ANUS", which really is just ['H','A','X',' ','M','Y',' ','A','N','U','S']?

FLATTEN MY ANUS