Iya~n, X no hou ja nakya?

Question:

Could you tell me what this means?
“iya~n, X no hou ja nakya, “Y ga suki” sicha dame dechuyo !”

And does “dechuyo” mean “desu yo”?
Why does one say “dechuyo” instead of “desu yo”?

Answer:

It's baby-talk.
“iya~n, X no hou ja nakya,": "Oh, nooo. I prefer X"

“Y ga suki” : "I like Y"

"XXXX sicha dame dechuyo !” : "You should not do XXX"
"dechuyo" is baby-talk of "dechuyo"