GROUP BY and SUM OVER Outputs

Given two SQL snippets using GROUP BY and SUM() OVER(), what are their outputs?

Asked in the First round stage. Use the sales table and evaluate these PostgreSQL queries:

SELECT department, SUM(amount) AS total_amount
FROM sales
GROUP BY department
ORDER BY department NULLS LAST;

SELECT department,
       SUM(SUM(amount)) OVER () AS grand_total
FROM sales
GROUP BY department
ORDER BY department NULLS LAST;

Output

1. Return both outputs in one result set with columns query_name, department, and result_value.
2. Label rows from the first query grouped_total and rows from the second query window_grand_total.
3. Preserve department ordering, with NULL departments last, and place the first query's rows before the second query's rows.