[u]Report_Time  M      I     Ta[/u]
02-SEP-13	X      Y	35167005
01-SEP-13	X      Y	35931902
03-SEP-13	X      Y	35931901

X Y 01-SEP-13 03-SEP-2013 35931902  35931901

SELECT m,
       i,
       min(report_time),
       max(report_time),
       min(ta) KEEP (DENSE_RANK FIRST ORDER BY report_time),
       max(ta) KEEP (DENSE_RANK LAST ORDER BY report_time)
FROM your_table
GROUP BY m,
         I

with 
  data as (
    select report_time, m, i ta,
           rank() over (order by report_time) rk1,
           rank() over (order by report_time desc) rk2
    from myTab
  )
select report_time, m, i ta
from data
where rk1=1 or rk2=1
/

with 
  data as (
    select report_time, m, i ta,
           rank() over (order by report_time) rk1,
           rank() over (order by report_time desc) rk2
    from myTab
  )
select report_time, m, i, MAX(CASE WHEN rk1=1 THEN ta END) ta1
MAX(CASE WHEN rk1=2 THEN ta END) ta2
from data
where rk1=1 or rk2=1
GROUP BY report_time, m, i
;

with data 
as
(
select report_time , m, i ,ta,
       rank() over (order by report_time ) rk1,
       rank() over (order by report_time desc ) rk2
from         sample_test
)
select  m, i , MAX(CASE WHEN rk1=1 THEN ta END) min_tac,
MAX(CASE WHEN rk2=1 THEN tac END) max_ta ,
max (case when  rk1=1 then report_time END ) min_rep , 
max (case when rk2=1 then report_time END) max_rep
from data
where rk1=1 or rk2=1
group by  m, i