SQL Server - Exclusive access could not be obtained because the database is in use

No, this has nothing to do with the version difference. The issue is exactly what the error message says: there are one or more processes active in this database. Well, active and active... If you have a query window open with this database as the current database that counts. Or you could have a node open in the database in Object Explorer. SQL Server don't want to make the decision to pull the rug for these processes itself, but if you know that it is OK, you can do this;

First, use the Script button on the top of the dialogue to script the RESTORE statement to a new query window. Then above the RESTORE command, add:

   USE db_to_restore  
   go  
   ALTER DATABASE db_to_restore SET SINGLE_USER WITH ROLLBACK IMMEDIATE  
   go  
   USE tempdb  
   go  
   ``  
   And please bear in mind that the current database will be entirely overwritten, so be careful!