Unlikely to be a network problem. SQL's behaviour on data modifications is all or nothing. If an insert fails, it fails, it doesn't succeed and leave some columns NULL.

The easiest (and safest) is to assume that all dynamic SQL is vulnerable, unless proven otherwise.

Anything that concatenates user input into a string and executes the resulting string is vulnerable. That includes user input that got stored in the database and then used to build...

No, that's declaring variables. (and no idea what the unknown language is doing)

Please have a look at the T-SQL documentation for creating procedures: https://docs.microsoft.com/en-us/sql/t-sql/statements/create-procedure-transact-sql

Table definitions and sample data please.

Please post table definitions and sample data (as INSERT statements) if you want a query written.

If you just want advice, then you can use ROW_NUMBER, partition by ContactID...

Collation won't allow SQL to return NOT ALLOWED if you filter for ALLOWED.
There's no filter for 'APPROVED' vs 'NOT APPROVED' in the WHERE clause, so SQL will return...

Table definitions please (as CREATE TABLE statement). And, if you look at the link, sample data is best as INSERT statements, so that testing queries is easy.
What is the...

Your preference.

If you drop the lookup table, make sure that you add constraints to the column. "Integrity enforced in the application" = "Garbage data eventually"
Also consider that ...

As Piet pointed out in your previous thread, people in general are not too keen on downloading excel spreadsheets. Please can you list your sample data and expected results as...