Just turns it into a different performance problem. One that's always bad, rather than bad depending on parameter passed, because the rows are estimated for <column> >= NULL, which always...

You need the certificate to be installed in master on the test instance to be able to restore.

Yes, you do want the logins from prod, or you'll have mismatched logins every single time that you do the restore to dev. That's what creating the logins from prod...

You do step 2 once. Not every time.
And you generate the login script from prod, not test. You want the logins on test to have the same sids...

What do you mean 'it doesn't reflect'?

I chatted with someone from SolarWinds. Please contact their customer support people and open a request to get this help file corrected

You could probably do it with a trigger, though will have to be complex and on both tables, and I don't know how you plan to have it automatically figure...

Asked and answered in another thread. https://www.sqlservercentral.com/Forums/2015957/How-to-create-Update-Store-Procedure-in-sql-between-two-table
Please in future stick to a single thread for a question

If you  format your code well, these missing brackets...

You're missing )) (two close brackets) after the END, just before the FROM

You do not. It's a system table, you can't even see it.
And note, it's not one index, your query aggregated 65 indexes into 2.

The problem with optional parameters like that is that they're a performance problem. Erratic performance, varying usually between moderately bad and very bad.
https://sqlinthewild.co.za/index.php/2018/03/13/revisiting-catch-all-queries/