Is there a way to create non-R2 databases in an R2 database server? I was hoping to do this in the compatibility options during the database creation, but only options are available for 2005 and 2000. Am I only stuck with installing the non-R2 SQL server to run side-by-side with my R2 database server?
No. Once a database has been attached to a version of SQL server, it can never be re-attached to a previous version, even if the compatibility level stays the same.
Yes.
There is no SQL 2008 R2 compatibility mode, only the SQL 2008 compatibility mode. This is because there are no syntax changes between SQL 2008 and SQL 2008 R2.