This is information not a question:
Yes I know, Oracle 8i is old and shout be replaced. But there companies, with legacy software.
When I read the Embarcadero information, It should work ( version 8.0.3 and later. (http://docwiki.embarcadero.com/RADStudio/Sydney/en/Connect_to_Oracle_Server_(FireDAC)) use: instantclient-basic-win32-11.1.0.7.0.zip), but you get the error: ORA-03134: Connections to this server version are no longer supported.
Testing with local sqlplus learned the error is generated in the oracle part. (instantclient). I have installed version 10.2.0.5 and sqlplus is working and fireDAC is working to .
For older oracle databases the info from Embarcadero is not correct. and you should use 10.2.0.5 version of the Oracle client part.