SQL> ed
Wrote file afiedt.buf

  1  with t(d,v1,v2) as(
  2  select date '2019-12-01',1,100 from dual union all
  3  select date '2020-11-01',1,200 from dual union all
  4  select date '2020-11-02',1,300 from dual union all
  5  select date '2020-11-15',0,400 from dual union all
  6  select date '2020-12-01',0,500 from dual union all
  7  select date '2020-12-05',0,600 from dual)
  8  select t.*
  9  ,FIRST_VALUE(v2) OVER (PARTITION BY to_char(d,'yyyymm') ORDER BY d  ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS first
 10  ,LAST_VALUE(v2) OVER (PARTITION BY to_char(d,'yyyymm') ORDER BY d  ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS last
 11  ,LAST_VALUE(decode(v1,1,v2) IGNORE NULLS) OVER (PARTITION BY to_char(d,'yyyymm') ORDER BY d  ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS last1
 12   from t
 13* order by 1
SQL> /

D                  V1         V2      FIRST       LAST      LAST1
---------- ---------- ---------- ---------- ---------- ----------
01.12.2019          1        100        100        100        100
01.11.2020          1        200        200        400        300
02.11.2020          1        300        200        400        300
15.11.2020          0        400        200        400        300
01.12.2020          0        500        500        600
05.12.2020          0        600        500        600

6 rows selected.