1) Yes its perfect copy. I think you can even do more than in real nand, but its developer stuff. (diosmios for example)
2) You must turn wii completely off (red light), if its not working I don't know, i never had that happen. But the wii won't boot again until you completely shut it down.
Bootmii shouldn't display anything when using sneek/uneek, it should just be black for moment and then go straight to system menu (or the health warning screen to be more exact).
Have you made sure you have game(s) in the USB HDD? DI-module will not work (it will black screen freeze) unless you...
You are 100% brickproof, you can have larger nand size, you can load games with DI module through official disc channel..
Plus some behind the scenes benefits, which I know nothing about, but for example, DIOS MIOS requires Sneek to work.
Wait in the HBC until the network icon stops blinking. If it remains dark, restart HBC. If it lights up, go to homebrew browser. Atleast works for me, it seems to have some issues with initializing the network, but if you let HBC handle that then it should work fine.
Your friend has no internet to come here and ask? Mainly because I would like to know reasons for doing this.
If he just "wants" it, he should just rehack it without cleaning, as the newer stuff overwrites the older..
If he actually has reason like "some sketchy stuff installed and doesn't...
I wouldn't tell them that it "was bricked by 4.3 update".
Sounds too knowledgeable.. Pretend to be dumb
Like say you tried to go to shop channel and it asked for update and you accepted and then it didnt work and wont boot.