listagg in order and including a sequence of separator when missing any row of a sequence
We have no problem with the aggregation but there is a special
  condition that we must follow. If a row or more rows, from sequence
  (R, D, K, N) for Atrib1, doesn't exist we must even include a set of
  ';' for each Atrib(1..4).


Suppose you have the following table (called TEST).  Some of the the "nrows" - N2, N3, N4, N5 - do not have a complete set of (R,D,K,N) values.

create table test ( nrows, a1, a2, a3, a4, final )
as
select 'N1', 'R', 'X', 'One', 'A1', 'True' from dual union all
select 'N1', 'D', 'Y', null, null, 'False' from dual union all
select 'N1', 'K', 'Z', null, null, 'False' from dual union all
select 'N1', 'N', 'A', null, null, 'True'  from dual union all
-- N2: D, K, N missing
select 'N2', 'R', 'X', 'two', 'B1', 'True' from dual union all
-- N3: R, K, N missing
select 'N3', 'D', 'Y', null, null, 'False' from dual union all
-- N4: D, R, N missing
select 'N4', 'K', 'Z', null, null, 'False' from dual union all
-- N5: D, K, R missing
select 'N5', 'N', 'A', null, null, 'True'  from dual ;


select * from test ;
NROWS  A1  A2  A3    A4    FINAL  
N1     R   X   One   A1    True   
N1     D   Y   NULL  NULL  False  
N1     K   Z   NULL  NULL  False  
N1     N   A   NULL  NULL  True   
N2     R   X   two   B1    True   
N3     D   Y   NULL  NULL  False  
N4     K   Z   NULL  NULL  False  
N5     N   A   NULL  NULL  True


As a first step, you could write a query that generates the missing nrows/A1 combinations (NA1), and LEFT JOIN it to the original (O) table. 

select *
from (  
  select nrows, a1
  from ( 
     select unique a1 from test 
  ) cross join (
     select unique nrows from test
  )
) NA1 
left join  (
   select nrows, a1, a2, a3, a4, final from test
) O
on NA1.nrows = O.nrows and NA1.a1 = O.a1 
;
-- result
NROWS  A1  NROWS  A1    A2    A3    A4    FINAL  
N1     R   N1     R     X     One   A1    True   
N1     D   N1     D     Y     NULL  NULL  False  
N1     K   N1     K     Z     NULL  NULL  False  
N1     N   N1     N     A     NULL  NULL  True   
N2     R   N2     R     X     two   B1    True   
N3     D   N3     D     Y     NULL  NULL  False  
N4     K   N4     K     Z     NULL  NULL  False  
N5     N   N5     N     A     NULL  NULL  True   
N2     K   NULL   NULL  NULL  NULL  NULL  NULL   
N2     N   NULL   NULL  NULL  NULL  NULL  NULL   
N4     D   NULL   NULL  NULL  NULL  NULL  NULL   
N3     R   NULL   NULL  NULL  NULL  NULL  NULL   
N2     D   NULL   NULL  NULL  NULL  NULL  NULL   
N3     N   NULL   NULL  NULL  NULL  NULL  NULL   
N3     K   NULL   NULL  NULL  NULL  NULL  NULL   
N4     N   NULL   NULL  NULL  NULL  NULL  NULL   
N4     R   NULL   NULL  NULL  NULL  NULL  NULL   
N5     D   NULL   NULL  NULL  NULL  NULL  NULL   
N5     K   NULL   NULL  NULL  NULL  NULL  NULL   
N5     R   NULL   NULL  NULL  NULL  NULL  NULL   
-- 20 rows selected. 


Then, use LISTAGG and DECODE (if CASE ... , as used in the example below, is too "bulky") and replace the NULLs with ;

select 
  NA1.nrows
, NA1.a1    as "RDKN"
, listagg ( O.a1 || ';' ||
    case when O.a2 is null then '' else O.a2 end || ';' ||
    case when O.a3 is null then '' else O.a3 end || ';' ||
    case when O.a4 is null then '' else O.a4 end || ';'
  , ';' ) within group ( order by O.a1 ) "Attribs 1-4"
from (  
  select nrows, a1
  from ( 
     select unique a1 from test 
  ) cross join (
     select unique nrows from test
  )
) NA1 
left join  (
   select nrows, a1, a2, a3, a4, final from test
) O
on NA1.nrows = O.nrows and NA1.a1 = O.a1 
group by NA1.nrows, NA1.a1
;


Result

NROWS  RDKN  Attribs 1-4  
N1     D     D;Y;;;       
N1     K     K;Z;;;       
N1     N     N;A;;;       
N1     R     R;X;One;A1;  
N2     D     ;;;;         
N2     K     ;;;;         
N2     N     ;;;;         
N2     R     R;X;two;B1;  
N3     D     D;Y;;;       
N3     K     ;;;;         
N3     N     ;;;;         
N3     R     ;;;;         
N4     D     ;;;;         
N4     K     K;Z;;;       
N4     N     ;;;;         
N4     R     ;;;;         
N5     D     ;;;;         
N5     K     ;;;;         
N5     N     N;A;;;       
N5     R     ;;;;         

20 rows selected. 


Tested with Oracle 12c, and Oracle 11g. Dbfiddle here.