Create table testdrop(ID Number,Name Varchar2(10), Comments Varchar2(100))

insert into testdrop values (1,'ABC','Test1; Test2:Test3')

insert into testdrop values (1,'XYZ','Test1; Test2:Test3')

select * from testdrop

insert into testdrop values (2,'DFG','T1;T2');
insert into testdrop values (2,'PQR','T1;T2');
insert into testdrop values (2,'LMN','T1;T2');
insert into testdrop values (2,'RST','T1;T2');
select * from testdrop;

with rws as (
select 
  distinct
  trim(regexp_substr(t.comments, '[^;:]+', 1, levels.column_value))  as error, 
  dense_rank() over (order by trim(regexp_substr(t.comments, '[^;:]+', 1, levels.column_value))) rn
from 
  testdrop t,
  table(cast(multiset(select level from dual connect by  level <= length (regexp_replace(t.comments, '[^;:]+'))  + 1) as sys.OdciNumberList)) levels
), t as (
  select t.*, row_number() over (order by id, name) rn from testdrop t
)
  select id, name, error from rws
  left join t partition by (id)
  on     rws.rn = t.rn
  order  by rws.rn;