Does updating wii remove homebrew
The Homebrew Channel may have been deleted if it was old and if so will need to be reinstalled.
Boot Mii as boot2 may have been removed and must be reinstalled.
Make a backup of your NAND with Boot Mii (preferably as boot2).
However, only perform this if you absolutely want the newer features.
Yes, although this tutorial no longer provides this information.
Updates check everything on your Wii to see if they have anything newer than what is installed. The chance of bricking via update is very, very small.
The 4.2 and 4.3 updates will detect old versions of IOS249 and/or IOS222/223 installed on your Wii and will thus indicate an update being necessary. You may have to reinstall some of your homebrew, though.