Can you sort the result in GROUP BY?

Question

I have two tables one is objects with the attribute of id and is_green.The other table is object_closure with the attributes of ancestor_id, descendant_od, and created_at. ie.

Objects: id, is_green

Object_closure: ancestor_id, descendant_od, created_at

There are more attributes in the Object table but not necessary to mention in this question.

I have a query like this:

    -- create a table
CREATE TABLE objects (
  id INTEGER PRIMARY KEY,
  is_green boolean
);
CREATE TABLE object_Closure (
  ancestor_id INTEGER ,
  descendant_id INTEGER,
  created_at date
);
-- insert some values
INSERT INTO objects VALUES (1, 1 );
INSERT INTO objects VALUES (2, 1 );
INSERT INTO objects VALUES (3, 1 );
INSERT INTO objects VALUES (4, 0 );
INSERT INTO objects VALUES (5, 1 );
INSERT INTO objects VALUES (6, 1 );
INSERT INTO object_Closure VALUES (1, 2, 12-12-2020 );
INSERT INTO object_Closure VALUES (1, 3, 12-13-2020 );
INSERT INTO object_Closure VALUES (2, 3, 12-14-2020 );
INSERT INTO object_Closure VALUES (4, 5, 12-15-2020 );
INSERT INTO object_Closure VALUES (4, 6, 12-16-2020 );
INSERT INTO object_Closure VALUES (5, 6, 12-17-2020 );
-- fetch some values
SELECT 
O.id,
P.id,
group_concat(DISTINCT P.id ) as p_ids
FROM objects O
LEFT JOIN object_Closure OC on O.id=OC.descendant_id
LEFT JOIN objects P on OC.ancestor_id=P.id AND P.is_green=1
GROUP BY O.id

The result is query result

I would like to see P.id for O.id=6 is also 5 instead of null. Afterall,5 is still a parentID (p.id). More importantly, I also want the id shown in P.id as the first created id if there are more than one. (see P.created_at).

I understand the reason why it happens is that the first one the system pick is null, and the null was created by the join with the condition of is_green; however, I need to filter out those objects that are green only in the p.id. I cannot do an inner join (because I need the other attributes of the table and sometimes both P.id and p_ids are null, but still need to show in the result) I cannot restructure the database. It is already there and cannot be changed. I also cannot just use a Min() or Max() aggregation because I want the ID that is picked is the first created one.

So is there a way to skip the null in the join? or is there a way to filter the selection in the select clause? or do an order by before the grouping?

P.S. My original code concat the P.id by the order of P.created_at. For some reason, I cannot replicate it in the online SQL simulator.