Real Application Clusters option included in SE. If you don't have shared storage for cluster, you can use Streams Replication, but SE supports only Synchronous Capture.
Yes, you can use this configuration. Oracle RAC is included in SE provided you use ASM as your shared storage. Then you will have to setup active-passive cluster to protect you database. Depend on your version of Oracle, here is an example https://blogs.oracle.com/xpsoluxdb/entry/clusterware_11gr2_setting_up_an_activepassive_failover_configuration
Hope that help,