Using hdparm to enable diabled features of a hard drive

[JD]

  When I issued
sudo hdparm -I /dev/hdb I got, among other info,
a list of commands/features, most of which are enabled,
except for a few. To wit:

Commands/features:
     Enabled    Supported:
        *    SMART feature set
             Security Mode feature set <<<<<<<
        *    Power Management feature set
        *    Write cache
        *    Look-ahead
        *    Host Protected Area feature set
        *    WRITE_BUFFER command
        *    READ_BUFFER command
        *    DOWNLOAD_MICROCODE
             SET_MAX security extension <<<<<<<<<<<<
        *    Automatic Acoustic Management feature set
        *    48-bit Address feature set
        *    Device Configuration Overlay feature set
        *    Mandatory FLUSH_CACHE
        *    FLUSH_CACHE_EXT
        *    SMART error logging
        *    SMART self-test
        *    General Purpose Logging feature set
        *    WRITE_{DMA|MULTIPLE}_FUA_EXT
        *    64-bit World wide name
             Write-Read-Verify feature set <<<<<<<<<<
        *    WRITE_UNCORRECTABLE_EXT command
        *    {READ,WRITE}_DMA_EXT_GPL commands
        *    Segmented DOWNLOAD_MICROCODE
        *    Gen1 signaling speed (1.5Gb/s)
        *    Gen2 signaling speed (3.0Gb/s)
        *    Native Command Queueing (NCQ)
        *    Phy event counters
             Device-initiated interface power management <<<<<<<<
        *    Software settings preservation
        *    SMART Command Transport (SCT) feature set
        *    SCT Long Sector Access (AC1)
        *    SCT LBA Segment Access (AC2)
        *    SCT Error Recovery Control (AC3)
        *    SCT Features Control (AC4)
        *    SCT Data Tables (AC5)
             unknown 206[12] (vendor specific)

So, my questions are:

a.  how can I use hdparm to enable write/read verify? That's what I am 
interested in.
      Man page does not mention this.
b. What is the effect of enabling "SET_MAX security extension", i.e.:
      hdparm --security-mode m  /dev/hdb
      What does it buy me?