(paranoia)
So I got a 3DS on 4.5 and a Gateway and got it all set up, but now my kids are like, "ooh, you got a 3DS. Now we can meet, Streetpass, multi-player..." etc. When I first set up my 3DS, I turned on the Parental Lock, locked everything, and didn't set up any wireless connections (shoot, I even make sure that the yellow wireless light is off before I begin playing.) But now I'm wondering if some/none/all of these features are safe to turn on. Obviously I don't intend to update my 3DS, but I've only had the console for about a week and don't know if it's possible for it to be accidentally updated other than with a cartridge.
tl;dr Which 3DS features (if any) should I avoid completely so as to not update past 4.5, and how likely is it to accidentally update my 3DS with the features (if any) that pose a likely threat of updating.
(/paranoia)
Apparently, setting parental controls on doesn't prevent downloading updates to the system/update prompts anymore.
Here, there are some individual points to consider in order to avoid downloading an update, sorted by effectiveness:
*Turn the wireless off forever.
*Delete any registered hotspot. Avoid Nintendo Zone areas.
*Connect to the internet only while playing a game. After exiting a game, make sure to disconnect the system from the internet by turning the wireless off or remaining far away enough from the area of the registered hotspot. Turn the wireless off when approaching to a Nintendo Zone.
About the infamous update prompt: Don't fear it...
It first asks for a confirmation to proceed, which can either be activated by presing A or by tapping the "OK" option.
Did you accidentally pressed A? Don't worry, it asks once again for confirmation. This time is showing the terms of the service and you can only accept them by tapping the "I accept" option. As you can see in the image, pressing A is no use, so it's impossible to "accidentally update".
After declining, it returns this screen and that's all.
As you can see, having the update prompt is not that bad. I have had it 7 months and is not really a problem to me.