Are you logged into your database with SYS AS SYSDBA?
At what point during the install do you encounter this error?
I think your main problem is: SP2-0310: unable to open file "coreins.sql"
According to the installation documentation you must change your working directory before calling sqlplus and the apexins.sql script.
Before running sqlplus change your directory:
Then you should run the apexins.sql script directly (no path prefix):
SQL> @apexins.sql APEX APEX TEMP /i/