BootNTR is not working for me... It says unknown FIRM, unknown home menu. Then does a dump. I am using BootNTR 3.4
Try the most recent
BootNTR Selector. It seems to be working just fine. Not that I've tested it extensively yet, but it boots into NTR just fine, the menu seems to work alright, etc.
There is any app to unable the update with the wi-fi turn on?
No apps I'm aware of. But you could use DNS servers. The same ones people use to keep the WiiU from updating will work, because they block the same servers -- 168.235.092.108 and 081.004.127.020
Keep in mind you won't be able to use Freeshop or CIAngel with these enabled. Online play should work, though I've not tested it. These may even prevent the system from phoning home when running homebrew CIAs online (again, not tested, if you get banned for running a homebrew CIA, don't blame me). I'm not saying it's safe to stream NTR with this, but safer than not using anything.
If you want to make sure you block them all, set the list on
this post up on your router. Or if you have no access to the router, my personal favorite trick, use
Simple DNSCrypt to block them, and enable the global option so your 3DS can connect through it, then just set your local DNSCrypt proxy up as both DNS servers. You should be using this anyway. It will prevent DNS leaks with a VPN. And if you're just using a browser proxy (even one that calls itself a VPN), you're still telling your ISP everywhere you're going via your DNS requests without this. DNSCrypt also prevents "man in the middle" attacks at public hotspots. There are versions available for Linux and Android as well. In short, everyone should use DNSCrypt. Especially everyone here in the US, where it is now legal for an ISP to sell your browsing habits to the highest bidder.