Month show in loop condition

declare
m varchar2(10);
mnyr date:=sysdate;
b date;
begin
for i in 1..12 loop
select last_day(mnyr),substr(last_day(mnyr),1,2) into b,m from dual;
mnyr:=add_months(mnyr,1);
b:=add_months(b,1);
dbms_output.put_line(m);
dbms_output.put_line(b);
end loop;
end;


declare
m varchar2(10);
mnyr date:='01-JAN-2015';
begin
for i in 1..12 loop
select substr(last_day(mnyr),1,2) into m from dual;
mnyr:=add_months(mnyr,1);
dbms_output.put_line(m);
end loop;
end;


declare
m varchar2(10);
mnyr date:='01-JAN-2015';
begin
for i in 1..12 loop
select last_day(mnyr) into m from dual;
mnyr:=add_months(mnyr,1);
dbms_output.put_line(m);
end loop;
end;


create or replace function date_check
return number is
m varchar2(10);
mnyr date:=sysdate;
begin
for i in 1..12 loop
select substr(last_day(mnyr),1,2) into m from dual;
mnyr:=add_months(mnyr,1);
return (m);
end loop;
end;


create or replace function date_check(mn date)
return number is
m varchar2(10);
mnyr date:=mn;
begin
select substr(last_day(mnyr),1,2) into m from dual;
return (m);
end;


declare
m number;
mnyr date:=sysdate;
begin
for i in 1..12 loop
select date_check(mnyr) into m from dual;
dbms_output.put_line(m);
mnyr:=add_months(mnyr,1);
end loop;
end;