Which four statements are true about database instance behavior? (Choose four.)

STARTUP NOMOUNT brings up a fully functional instance (SGA and background processes); an 'idle instance' typically refers to the state before any STARTUP command, where only a connection to the software exists without an active instance.

Not all V$ views return data in NOMOUNT or MOUNT states, as many require the database to be open to access actual database file information or session activity.

Although full data block consistency checks occur during the OPEN phase, the MOUNT operation implicitly verifies the control file's integrity and its ability to properly identify and locate the registered redo logs and data files, which is a form of consistency check necessary for database startup.

In the MOUNT state, the database control file is read, but data files and redo log files are not yet open, allowing administrative commands like ALTER DATABASE RENAME FILE to modify their paths within the control file.

An SPFILE is a server parameter file which is read during instance startup; even when connected to an idle instance (before STARTUP NOMOUNT), the SPFILE is accessible as a regular file and can be updated using ALTER SYSTEM SET ... SCOPE=SPFILE.

Similar to redo log files, data files are known but not open in the MOUNT state, which enables administrative operations such as renaming their physical location using the ALTER DATABASE RENAME FILE command.