ORDER BY items must appear in the select list if SELECT DISTINCT is specified
The real issue is caused by data type conversion. If you add this expression to the select list:

CASE WHEN c.ID &gt; 10 THEN c.Title
        ELSE c.ID
        END


you will see another error. Something like: "Conversion failed when converting the nvarchar value 'Some title' to data type int". According to data type precedence when you compare varchar with int values (SQL Server will need to compare Title with ID to sort your final result set) varchar should be converted to int because int has higher precedence.
https://docs.microsoft.com/en-us/sql/t-sql/data-types/data-type-precedence-transact-sql?view=sql-server-ver15