I have two sql server instances, on is SQL Server 2008 R2, one is the first release of SQL Server 2008 ("R1"), is it possible to log ship from the R2 machine to the R1 machine?
If is not possible, is mirroring possible?
If that is not possible, is there another MS supported solution for replication between R1 and R2?
No, since you can't restore a backup from R2 on "R1" it will not work with either log shipping or mirroring.
Replication works between versions.