Sample string: AA^Col1^Col2^Col3^Col4^Col5 

AA^Col1^Col2^Col3^Col4 

SCOTT@orcl_12.1.0.2.0> select regexp_substr ('AA^Col1^Col2^Col3^Col4^Col5', '([^\^]+\^){4}?[^\^]+') as output
  2  from   dual
  3  /

OUTPUT
----------------------
AA^Col1^Col2^Col3^Col4

1 row selected.

SQL> select regexp_replace('AA^Col1^Col2^Col3^Col4^Col5','\^[^^]*$') from dual;
REGEXP_REPLACE('AA^COL
----------------------
AA^Col1^Col2^Col3^Col4

with t as (select 'AA^Col1^Col2^Col3^Col4^Col5' val from dual)
select substr(val, 1, instr(val, '^', -1)-1)
from t