Downgrading to 4.2 will get you nowhere. Following the Softmod ANY Wii guide (link in my sig) will put you on 4.1, which is the recommended SM version. Since you start on 4.3 you will be able to play all new games even if you downgrade.. The guide will also tell you how to block online/disc updates, so no worries there. All your apps (emulators, USB loaders, etc) will work just fine.