Performing join on 3 tables & retrieving selected columns

This uses the same basic technique as jonearles ⁽⁺¹⁾ (since removed) but eliminates the PIVOT and would require only one function that turns the string into a CASE statement.

SELECT substr(
      MIN (
         CASE WHEN Blank=1 THEN '1 Blank' 
              WHEN Error=1 THEN '2 Error' 
              WHEN InProgress=1 THEN '3 InProgress' 
              WHEN Completed=1 THEN '4 Completed' 
         END
         )
   ,3) state_code
FROM m_object mo
JOIN m_form mf ON mo.id = mf.id
WHERE mo.v = :2 AND mf.formlayout_id = :1;  

I assume the data looks something like this:

drop table m_object;
create table m_object as 
   (select 10 id, 0 blank, 0 error, 0 inprogress, 1 completed, 99 v from dual);
insert into m_object values (11,1,0,0,0,99);
insert into m_object values (12,0,0,0,1,99);
insert into m_object values (13,0,1,1,0,99);

drop table m_form;
create table m_form as (select 10 id, 20 formlayout_id from dual);
insert into m_form values (11,21);
insert into m_form values (12,22);
insert into m_form values (13,20);

Here is what the function might look like if it were done in PL/SQL. It was just thrown together and is only meant to illustrate building the SQL statement and is not meant to be an example of good coding.

set serveroutput on format wrapped

DECLARE
vPassed Varchar2(500) := 'Blank,Error,InProgress,Completed';

   Function MakeCase(pOriginal In Varchar2) Return Varchar2 Is
      vBuilt     Varchar2(500);
      vWord      Varchar2(100);
      vChar      Char(1);
      vWordCount Number(1) := 1;
   Begin
      For vLoop In 1..Length(pOriginal) Loop
         vChar := substr(pOriginal,vLoop,1);
         If (vChar = ',') Then
            If (vBuilt IS NULL) Then
               vBuilt := 'CASE WHEN ';
            End If;
            vBuilt := vBuilt || vWord || '=1 THEN '''
               || to_char(vWordCount,'FM0') || ' ' || vWord || ''' WHEN ';
            vWord := '';
            vWordCount := vWordCount + 1;            
         Else                  
            vWord := vWord || vChar;            
         End If;
      End Loop;
      vBuilt := vBuilt || vWord || '=1 THEN ''' 
         || to_char(vWordCount,'FM0') || ' ' || vWord || ''' ';
      vBuilt := vBuilt || ' END ';
      Return vBuilt;
   End;

BEGIN
   vPassed := MakeCase(vPassed);
   DBMS_Output.Put_Line(vPassed);

   --Use vPassed here to build SQL statement.
END;
/

Logically the joins are resolved in the order of the ON clauses from left to right.

The output of each join is a virtual table that goes into the next join.

So for the query in your question the virtual table result of A LJ B is then right joined onto C. The join condition of B.Col3 = C.Col4 will lose any null extended rows preserved by the original left join effectively turning the first join back into a inner join and the resulting virtual table (which preserves all rows from C) is then inner joined onto D.

So your initial query can be simplified as

SELECT *
FROM TBLA A
INNER JOIN TBLB B ON A.Col1 = B.Col2
RIGHT JOIN TBLC C ON B.Col3 = C.Col4
      JOIN TBLD D ON C.Col5 = D.Col6

Which is effectively the same as (A IJ B) ROJ (C IJ D)

The order of the ON clauses is not necessarily the same as the order the tables appear in the query. This could also be rewritten as (C IJ D) LOJ (A IJ B)

SELECT *
FROM   TBLC C
       INNER JOIN TBLD D
         ON C.Col5 = D.Col6
       LEFT JOIN TBLA A
                 INNER JOIN TBLB B
                   ON A.Col1 = B.Col2
         ON B.Col3 = C.Col4 

The position of the on clauses means that the outer join is carried out between the two virtual tables resulting from (C IJ D) and (A IJ B) rather than just on a single table.

In your second query conceptually the virtual table A x C is left joined onto B preserving the entire cartesian product then the result of that is joined onto D with the predicate C.Col5 = D.Col6. This eliminates any rows from the final result that do not inner join between C and D meaning it is equivalent to

SELECT *
FROM   TBLC C
       JOIN TBLD D
         ON C.Col5 = D.Col6
       CROSS JOIN TBLA A
       LEFT JOIN TBLB B
         ON A.Col1 = B.Col2
            AND B.Col3 = C.Col4