Oracle Database Discussions

Hello,
now I'm planning to practice downgrading my Oracle 10g (10.2.0.4.0) to 9i. The server is AIX.
The COMPATIBLE parameter is already 9.2.0.0.0
I've read the procedure to do this in
http://download.oracle.com/docs/cd/B19306_01/server.102/b14238/downgrade.htm#i1010243

But, I little bit confuse about my understanding on point 14 in topic "Downgrade the Database". It says:

"14. Restore the configuration files (for example, parameter files, password files, and so on) of the release to which you are downgrading."

These are my questions:
1. How to restore them ? Just copy the files from Oracle 10g home to Oracle 9i home ?
2. If so, what files are needed ? is it enough just parameter file (initSID.ora) and password file (orapwSID) in directory ORACLE_HOME/dbs ? or any other things ?

Please advice :)

Thanks,
BSS.