Why doesn’t row data show up in SQL Developer

If you've no need to store the date component, then an interval day(0) to second is the most practical approach. The biggest advantage comes if you need to do any calculations finding how long has elapsed between two times as you don't need to do any extra processing out of the box.

For example:

create table times ( t1 interval day(0) to second, t2 interval day(0) to second);

insert into times values ( interval '0 09:30:00' day(0) to second, interval '0 12:30:00' day(0) to second);
insert into times values ( interval '0 10:30:00' day(0) to second, interval '0 13:45:00' day(0) to second);
insert into times values ( interval '0 11:30:00' day(0) to second, interval '0 12:05:01' day(0) to second);

commit;

SELECT * FROM times
where  t1 between interval '0 10:00:00' day to second and interval '0 11:00:00' day to second ;

T1          T2        
----------- -----------
0 10:30:0   0 13:45:0   

SELECT max(t2-t1) FROM times; 

MAX(T2-T1)
-----------
0 3:15:0.0  

You also have standard functions to extract the various components of the time (hour, minute, etc.):

SELECT extract(hour from t1) hr, extract(minute from t1) mn, extract(second from t1) sec
FROM times; 

        HR         MN        SEC
---------- ---------- ----------
         9         30          0 
        10         30          0 
        11         30          0 

1) If you want the headings in one line, you have to use a UNION with a select from dual. Example:

select '"'||'col1'||'","'||'"col2"'||'","'||'"col3"'
  from dual
union
select '"'||col1||'","'||col2||'","'||col3||'"'
  from table;

2) This one is tricky. It helps to know what ascii character your line breaks actually are. Depending on how they were written, generally (but not always) they will be chr(10) or a combination of chr(10)chr(13). You can use the REPLACE function in your query to replace those with '', which should get rid of them.

3) If you want quotes, see my example #1 above.

HTH.