Do Chosen-Chiphertext attacks only apply to public-key cryptosystems? Do Chosen-Chiphertext attacks (CCA-1/2) only apply to public-key Cryptosystem?
No, there are also CCA games for private key encryption schemes. There you have additional encryption oracles that you can use, to obtain encryptions for messages of your choice (in a private key encryption scheme you can not encrypt yourself, because this requires the secret key).
See here for a concise explanation and comparison:
http://crypto.cs.uiuc.edu/wiki/index.php/IND-CCA