The RECOVER STANDBY DATABASE FROM SERVICE command in RMAN is designed to automate various steps required to recover the standby database, especially when dealing with an archive gap. When this command is executed, the following actions can occur automatically:
Remember all data file names on the standby (1): RMAN has the capability to recall the names and paths of all data files associated with the standby database.
Restart standby in nomount (2): The standby database can be automatically restarted in the NOMOUNT state, allowing recovery operations to proceed without the database being open.
Restore controlfile from primary (3): RMAN can restore the control file from the primary database to the standby system, ensuring that the standby has the most up-to-date control file.
Mount standby database (4): After restoring the control file, the standby database is mounted to prepare for data file recovery.
Rename data files from stored standby names (5): Not typically done automatically by this command.
Restore new data files to new names (6): New data files added to the primary since the last synchronization can be restored to the standby with their correct names.
Recover standby (7): Finally, RMAN will apply any necessary redo logs to bring the standby database up to date with the primary.
While some steps, such as renaming data files (5), typically require manual intervention or scripting, most of the recovery process can be handled by RMAN automatically, streamlining the recovery of the standby database.
Reference:
Oracle Database Backup and Recovery User's Guide
Oracle Data Guard Concepts and Administration Guide

Automatic Block Media Recovery can be a significant feature for maintaining data integrity within a Data Guard configuration.
* A corrupt block on the primary database can be automatically recovered, using a block from a standby database with Real-Time Query enabled (A): When a corrupted block is encountered on the primary database, Oracle can automatically replace it with a good block from the standby database where Real-Time Query is enabled, leveraging the standby as a source of good data.
* A corrupt block on the primary database is automatically recovered, using a block from a flashback log from the primary database (E): If a good block version is available in the flashback logs of the primary database, Automatic Block Media Recovery can use it to recover the corrupted block on the primary.References:
* Oracle Database Backup and Recovery User's Guide

When setting up a Data Guard Broker configuration for a primary database and its physical standby, the following prerequisites must be met:
A: Oracle Net connectivity must be defined on both the primary and standby hosts to enable the respective database instances to communicate with each other.
B: Supplemental logging is required on the primary database because it provides additional logging necessary for the standby database to be able to apply changes from the primary database accurately.
F: The DG_BROKER_START parameter must be set to TRUE for both the primary and standby database instances. This parameter is used to start the Data Guard Broker process which manages the configuration.
Options C and D are not prerequisites for creating a Data Guard Broker configuration. Additionally, while FORCE LOGGING mode (option E) is recommended as a best practice to prevent possible data inconsistencies during media recovery, it is not a strict prerequisite for creating a Data Guard Broker configuration.

DB_NAME (A): The name of the database, which should remain consistent across the primary and standby databases.
db_file_name_convert (C): This parameter helps define the mapping of data file names from the primary to the standby database, which is crucial during the creation and operation of a standby database.
COMPATIBLE (D): The compatibility level can influence the features that can be used on the standby database and must be consistent with or higher than that of the primary database, especially after upgrades.
STANDBY_ARCHIVE_DEST (F): This parameter specifies the destination of archived redo log files on the standby database, which is important for log transport and apply services.
Reference:
Oracle Data Guard Concepts and Administration Guide
Oracle Database Reference

To enable Fast-Start Failover in a Data Guard environment, the following conditions must be in place:
* The Data Guard environment must be managed by the Data Guard Broker (A): The Broker simplifies management tasks and is required to enable fast-start failover, which is an automatic failover mechanism provided by Data Guard.
* You can specify only one standby database as the fast-start failover target (C): Fast-start failover is designed to fail over to a single, predetermined standby database, known as the target standby.
* Flashback Database must be enabled on both the primary database and the Fast-Start Failover target standby database (F): Flashback Database provides a quick way to revert a database to a point
* in time before a logical or physical corruption or error occurred. It must be enabled on both the primary and target standby databases to allow for the possibility of reinstating the old primary as a standby after a failover.References:
* Oracle Data Guard Concepts and Administration Guide
* Oracle Database High Availability Overview