with t as 
( select 'demo staging1 abc' a from dual
union 
select 'demo staging2 abc' a from dual
union 
select 'demo staging3 abc' a from dual
union 
select 'demo staging efg' a from dual
union 
select 'demo staging ijk' a from dual
union 
select 'demo staging lmn' a from dual)
select * from t;

SQL> with t as
  2  ( select 'demo staging1 abc' a from dual
  3  union
  4  select 'demo staging2 abc' a from dual
  5  union
  6  select 'demo staging3 abc' a from dual
  7  union
  8  select 'demo staging efg' a from dual
  9  union
 10  select 'demo staging ijk' a from dual
 11  union
 12  select 'demo staging lmn' a from dual)
 13  select * from t
 14  order by sign(instr(a,'abc')) desc, a
 15  /
A
-----------------
demo staging1 abc
demo staging2 abc
demo staging3 abc
demo staging efg
demo staging ijk
demo staging lmn