sry but there isnt codes for the snow field or the beach... :(
but to unlock the beach u breed w/ the dog wearing to blue and white striped suit. to unlock the snow field u have to breed w/ the dog wearing the pink ski suit thing.
heres some codes to unlock stuff:
dgsrck
ilovev
havfun
oceanw
christ
dumbel
thats all i no but if u see everyone elses comments they have A LOT more. these r the only ones i can remember but i used other pplz codes too...

hope this helps!

~white wolf lover