[Security Discussion] Koloktos:
I don't think I'm allowed to directly post photos here yet, but I've uploaded a bunch to an Imgur album in the 'code' tag below. The "Developer Diagnosis Top" menu (what Honda calls), allows access to the Android 'Developer Settings' menu. I also snapped a bunch of pics of some other menus/settings. There was also a 'Boot Mode Select' which I'll go into detail about that below in the Developer Options section.

Album:

imgur.com/a/5VoIp

USER DATA IMPORT / EXPORT:

In the "Detail and Information Setting" menu (aka, the menu you access via Power+Menu+Brightness) there's a submenu which allows you to import & export your user settings to USB. I did an export and it saves in an XML format to an attached USB disk. There was two settings that caught my eye in that file:

<CARPLAY_ONOFF>1</CARPLAY_ONOFF>

<ANDROID_AUTO_ONOFF>1</ANDROID_AUTO_ONOFF>

Unfortunately, while you can modify the XML file and use the IMPORT function to attempt to update your settings, the entire XML file appears to have some kind of checksum noted at the end of the file. The import does not throw any errors, but the settings do not update. I tried doing an export after the import to double check to see if any settings took, but the export after the import rendered the same file shown below.

The XML file starts with SIG and ends with a magic number, which in my case was 8c97. If someone can figure out how to checksum/hash/math/domagic to yield that number, then we can modify the CARPLAY_ONOFF and the ANDROID_AUTO_ONOFF tags to 0. It's also worth noting that the XML tags ending in _ONOFF that: 0='ON' and 1='OFF'.

SIG<CLOCK_DISPLAY_TYPE>2</CLOCK_DISPLAY_TYPE>
<CLOCK_BACKGROUND>3</CLOCK_BACKGROUND>
<CLOCK_TIME_ZONE_AUTOMATIC>0</CLOCK_TIME_ZONE_AUTOMATIC>
<CLOCK_SUMMER_TIME>1</CLOCK_SUMMER_TIME>
<CLOCK_OFFSET_ADJUSTMENT>0</CLOCK_OFFSET_ADJUSTMENT>
<CLOCK_AUTO_SMARTPHONE_LINKAGE_SETTING>1</CLOCK_AUTO_SMARTPHONE_LINKAGE_SETTING>
<CLOCK_DISPLAY_ONOFF_SETTING>1</CLOCK_DISPLAY_ONOFF_SETTING>
<CLOCK_DISPLAY_POSITION_SETTING>1</CLOCK_DISPLAY_POSITION_SETTING>
<INFOSETTING_INFO_TOP>2</INFOSETTING_INFO_TOP>
<INFOSETTING_INFO_TOP_LAST_SELECTED_ITEM>2</INFOSETTING_INFO_TOP_LAST_SELECTED_ITEM>
<INFOSETTING_INFO_MENU_LAST_SELECTED_ITEM>2</INFOSETTING_INFO_MENU_LAST_SELECTED_ITEM>
<DISCLAIMER_TARGET_INFOMATION_COLLECT>1</DISCLAIMER_TARGET_INFOMATION_COLLECT>
<TRACK_MODE_DISPLAY>1</TRACK_MODE_DISPLAY>
<ETC_GUIDE>1</ETC_GUIDE>
<COLLISION_PREVENTION>1</COLLISION_PREVENTION>
<SIGNAL_OVERSIGHT_PREVENTION>1</SIGNAL_OVERSIGHT_PREVENTION>
<PAUSE_REGULATION_OVERSIGHT_PREVENTION>1</PAUSE_REGULATION_OVERSIGHT_PREVENTION>
<ENCOUNTER_PREVENTION>1</ENCOUNTER_PREVENTION>
<MEMORY_LAST_SCREEN_SETTING>0</MEMORY_LAST_SCREEN_SETTING>
<MENU_COLOR>1</MENU_COLOR>
<VERBAL_REMINDER>1</VERBAL_REMINDER>
<PARKING_BRAKE_CAUTION>1</PARKING_BRAKE_CAUTION>
<SEAT_BELT_CAUTION>1</SEAT_BELT_CAUTION>
<STARTUP_LAST_ECO_INFORMATION_DISPLAY>1</STARTUP_LAST_ECO_INFORMATION_DISPLAY>
<VOICE_RECOGNITION_TUTOR>1</VOICE_RECOGNITION_TUTOR>
<VOICE_ONE_PUSH>1</VOICE_ONE_PUSH>
<SONG_BY_VOICE>1</SONG_BY_VOICE>
<VOICE_COMMAND_READ>1</VOICE_COMMAND_READ>
<VEHICLE_ONOFF>0</VEHICLE_ONOFF>
<AUDIO_SOURCE_POPUP>1</AUDIO_SOURCE_POPUP>
<LOCATION_SERVICE_TYPE>1</LOCATION_SERVICE_TYPE>
<PERMANENTLY_WITH_AGREEMENT>1</PERMANENTLY_WITH_AGREEMENT>
<CSF_ONOFF>1</CSF_ONOFF>
<SNAPSHOT_ONOFF>0</SNAPSHOT_ONOFF>
<PANDORA_ONOFF>1</PANDORA_ONOFF>
<HIR_ONOFF>1</HIR_ONOFF>
<ARTWORK_ONOFF>1</ARTWORK_ONOFF>
<LAST_FUNCTION>2</LAST_FUNCTION>
<LAST_APPLICATION></LAST_APPLICATION>
<AUDIO_LAST_MODE>0</AUDIO_LAST_MODE>
<SNAPSHOT_BMP_FORMAT>1</SNAPSHOT_BMP_FORMAT>
<ASPECT_RATIO_USB>0</ASPECT_RATIO_USB>
<ASPECT_RATIO_HDMI>1</ASPECT_RATIO_HDMI>
<CLIMATE_SCREEN_TIMEOUT>2</CLIMATE_SCREEN_TIMEOUT>
<CARPLAY_ONOFF>1</CARPLAY_ONOFF>
<ANDROID_AUTO_ONOFF>1</ANDROID_AUTO_ONOFF>
<ETC_DSRC_UPLINK>0</ETC_DSRC_UPLINK>
<ASPECT_RATIO_DVD>2</ASPECT_RATIO_DVD>8c97

DEVELOPER OPTIONS / BOOT MODE SELECT:

This is accessible via: 'Developer Diagnosis Top' menu --> 'Android Settings' --> 'Developer Options'

Once here you can enable USB debugging, install certificates, etc. There's also a "Boot Mode Select" option in 'Developer Settings'. This brings you to a screen which allows you to select one of four options:

Uploader

USB Boot

SD Boot

Mode Clear

You can click any of the first three options and it will give you a popup letting you know the boot mode has changed. This won't take effect until you restart the car. If you haven't restarted yet but have chose a boot mode option, you can reset it back to normal boot by clicking 'Mode Clear'. Also in this menu has some options regarding 'Snap Shots', which also have their own menu in the Developer Diagnosis Top menu. I did not have a chance to play around with these or export a snapshot. I'll try and grab one later this week.

A word of caution regarding boot modes: be careful with these boot mode options. The last thing I did tonight was decide to give the 'Uploader' option a shot, and restarted the car to apply the boot mode change. The car still functions perfectly after the restart, the 'Honda Link' image pops up on the touchscreen, but the screen remains blank. My guess is that this is similar to Androids 'Recovery Mode', however no text is visible on the screen. I tried a bunch of key combos to try to exit but did not have any luck. On a positive note, this could allow updates directly from ADB through the 'hidden USB' (which allows ADB access, this port is supposedly accessible by taking out the head unit) that a member described on another thread on this site. The 3x main USB ports (2 under radio, 1 in center console) do not work with ADB. I tried this earlier both before and after entering Uploader boot mode to confirm this.

If someone can figure out how to get that checksum/magic number above, that'd be a big step forward. It'd also be nice to know how to exit the boot modes once you enter into them without using the ADB USB port (perhaps some key combo similar to Android phones?) I'll tinker some more with this later in the week, but if someone figures out something before then, please advise.

Lastly, I would have added notes to each photo but it's getting late here. If anyone has any questions regarding the album, feel free to ask.