The SELECT INTOs will hold locks.  Those might be causing issues.

One good way to avoid that is to an initial SELECT TOP (0) ... INTO to create the table, then...

Wow, that's exceptional.  I've never been at a place that had, say an "order" table vs. an "orders" table.

I wasn't sure StatusDate included a time.  If it's just a date, it's not safe to ORDER BY it.

I believe the more common, and better, naming for tables is plural.  I can't think of a major relational dbms that uses singular system table names.

For example: sys.objects (SQL Server),...

Yep, definitely remove ID.  The key to a "relationship" table should be the relationship keys, NOT an ID column.

;WITH ctePrevPrStatus AS (
    SELECT *, LAG(PrStatus) OVER(PARTITION BY PrID ORDER BY StatusID) AS PrPrevStatus
    FROM dbo.tblPresentationStatus
)
SELECT *
FROM ctePrevPrStatus
WHERE 
 ...

I'd suggest the clustered index on ( trade_date, symbol ) and not the other way around.  You want the clus key to be unique, so, if it's not, you'll want...

The TaskNames would have to be contiguous for that method to work.  I wanted to also handle some other TaskName appearing between "Distribute" and "Print", just in case.

SELECT JobID
FROM dbo.tblPrintTask
GROUP BY JobID
HAVING MAX(CASE WHEN TaskName = 'Distribute' THEN TaskID END) < 
    MAX(CASE WHEN TaskName = 'Print' THEN TaskID END)

(page bump needed?)

You could easily have an order of magnitude more rows in SG table than in T, and if you have a phone app waiting for the response, I would still...

Nice.

Also, you don't have to change the FKs in other tables if you need one for just ID.  Instead, just add a unqiue nonclus index on ( ID ); it...

> What difference the client is a phone? <<

Because to determine all the Tests that haven't been fully graded could require scanning a very large number of StudentGrade rows.

If, instead,...

I would use option 2 in this case.  The safest way to set the flag consistently accurately is to use a trigger on the StudentsGrade table.

SQL captures the size of backups in table msdb.dbo.backupset.  Thus, you can query that table to add up total space used for backups.