Determine the SQL Server version and edition from the available set up, before actually installing it?
To answer your first question :

If you are not sure, then just manually  launch the setup.exe and verify. 

When you launch SQL Server 2008 installation using setup.exe, you will see: 



Below is for SQL Server 2008R2 :



An alternative to running the setup executable, is to right click and look for the version there. It'll be something like 10, 10.50, 11, etc. so you do need to convert

To answer your second question :

From SQL Server 2008 and up, Microsoft has changed as the edition depends on the PID that can be found in DefaultSetup.ini. The DefaultSetup.ini for SQL Server 2008 and 2008R2 has same format. So essentially if you don't know, you have to make sure that you have the correct installation files.

;SQLSERVER2008 Configuration File
[SQLSERVER2008]
PID="xxxxx-xxxxx-xxxxx-xxxxx-xxxxx"


For SQL Server 2005, it was stated in the Servers folder default.htm. See

How to tell what edition your SQL Server setup files are

I don't think you can guess from the PID a particular edition of SQL Server. A full media will be good for all editions of a particular SQL Server version.