1. Make sure all your stored procedures are in source control.
2. For each stored procedure you should have a script like this:
IF OBJECT_ID('dbo.myStoredProcedure','P') IS NULL 
 ...

https://www.mssqltips.com/sqlservertip/2964/encrypting-and-decrypting-sql-server-stored-procedures-views-and-userdefined-functions/

If you want to improve performance on selects (not updates and inserts) you can create the function with schemabinding, then you can persist the column:
ALTER FUNCTION...

Why doesn't it come up with: 
45,27
45,50
45,45
?
Can you provide your cursor solution so we can convert it to a set solution?

You should read this thread: https://www.sqlservercentral.com/Forums/2008959/does-use-of-large-datatypes-where-much-smaller-ones-will-do-affect-performance

You can set up perfmon to monitor CPU usage. for a few days then look at the plot.
If you have enterprise version of SQL Server you can create an...

If you want them in a certain order:SELECT TOP (1) Field
FROM myTable
ORDER BY CASE WHEN Field='BRA' THEN 1
     WHEN Field='CHL' THEN 2

CREATE FUNCTION ConvertToBase64
(
    @P1 varchar(100)
)
RETURNS nvarchar(100)
AS
BEGIN
    DECLARE @ResultVar nvarchar(MAX)

    SELECT @ResultVar=CAST(N'' AS XML).value('xs:base64Binary(xs:hexBinary(sql:column("P1")))', 'VARCHAR(MAX)')
  FROM (SELECT CONVERT(VARBINARY(MAX),@P1) [P1]) X

    RETURN...