Using map_agg with order in Athena Presto

Question

I'm aware of using ORDER BY in window queries when you use array aggregations, but how do you order this in combination with a group by?

Specifically, I want to make sure rooms and dates are ordered so that I can use that in a subsequent query. For example in the query below they need to be of descending order to make the search work :)

Alternatively, are maps ordered, or do they have no order?

WITH mapped as (
    SELECT
        guestid,
        map_agg(room, startdate) as startdates,
        array_agg(startdate) as dates,
        array_agg(room) as rooms
    FROM (VALUES 
        (1, 'room 1', date('2024-01-01')),
        (1, 'room 2', date('2024-01-10')),
        (1, 'out', date('2024-01-20')),
        (2, 'room 2', date('2024-01-10')),
        (2, 'room 1', date('2024-01-25')),
        (2, 'out', date('2024-02-10'))
    ) AS checkins(guestid, room, startdate)
    GROUP BY guestid
)
SELECT 
    guestid, 
    dt_utc, 
    rooms,
    dates,
    array_position(transform(dates, d -> d <= dt_utc), true) as p
    -- , rooms[p]
FROM mapped 
CROSS JOIN (VALUES 
    (date('2024-01-02')),
    (date('2024-01-12')),
    (date('2024-02-11'))
) AS dates(dt_utc)