The parameters that you posted, are they from 12c host, right?
Did you set the SQLNET.ALLOWED_LOGON_VERSION=8 on the 9i server also?
Yes this parameter I have set only oracle 12c.
No I did not set it on 9i DB sqlnet.ora file.
Shall I add it on Oracle 9i DB sqlnet.ora file below line :
Yes, you should.
Take a look also, on the password_versions for the user that you're trying to connect.
How did you resolve the problem ?