Alright some answers that I hope will help you!
I have heard of such an app but have not used on due to my Nexus 10 being SD cardless without a cardread and OTG cable but, I did come across this thread.
[APP] GatewayFlash
"GatewayFlash is an app I've written for rooted Android devices. It allows you to flash new ROMs onto your microSD card straight from your phone/tablet. Convenient if you don't want to carry around tons of microSD cards for all your games!"
Yes it is possible, I have done that and even used the emuNAND and flashed it to my real NAND to play pokemon X/Y online. It's possible to switch images for now (who knows what the future holds). The dumps only work for that particular 3DS due to per console encryption and I recommend taking more then one dump of your original at different points in time, kinda paranoia but better safe then sorry. I have gone from 2.2.0 -> 4.5.0 -> 7.1.0 then back to 2.2.0 works just fine.
Check this lovely thread for unbricking 3DS unbricking progress so far the raspberry pi seems to work well by all accounted test of it, thank you bkifft.
So I was gonna make a new thread but I decided I'd give the noon paradise a try... My question is ... Since you can only have one ROM on your gateway card is there some sort of application for an android phone like windows disk imager 32 so that I can write a game to an SD card from my phone? Thanks for the reply in advance
I have heard of such an app but have not used on due to my Nexus 10 being SD cardless without a cardread and OTG cable but, I did come across this thread.
[APP] GatewayFlash
"GatewayFlash is an app I've written for rooted Android devices. It allows you to flash new ROMs onto your microSD card straight from your phone/tablet. Convenient if you don't want to carry around tons of microSD cards for all your games!"
So, to summrarize:
Hardware mod dump 4.4.0 NAND -> update to latest System Menu and dump NAND again.
Switch between NAND images for different use cases. Possible?
Unbrick using Arduino/Raspi. Possible?
Yes it is possible, I have done that and even used the emuNAND and flashed it to my real NAND to play pokemon X/Y online. It's possible to switch images for now (who knows what the future holds). The dumps only work for that particular 3DS due to per console encryption and I recommend taking more then one dump of your original at different points in time, kinda paranoia but better safe then sorry. I have gone from 2.2.0 -> 4.5.0 -> 7.1.0 then back to 2.2.0 works just fine.
Check this lovely thread for unbricking 3DS unbricking progress so far the raspberry pi seems to work well by all accounted test of it, thank you bkifft.