Backspace, Delete and Cursor keys should work beforehand.
Useful environment settings include (using bash):
ORACLE_BASE=/app/oracle/1120/db (or similar)
SQLPlus can be configured by a "login.sql" file, located in the current directory when calling sqlplus.
Useful settings include:
set pagesize 0
With these settings, "ed" and "r" command should work.
Command completion can be achieved by installing RLWRRAP and the sqlplus rlwrap extensions.
These can be found at Linuxification.AT
Rlwrap is a GNU readline library wrapper and can be found here
Readline-6.1 packages for Solaris are available from OpenCSW.