Downgrade 3.4 to 3.2

There is no boot IOS. All of the IOSs (and then the system menu) are loaded simultaneously during boot2, the third stage of the Wiis boot processes.

The IOS controlls Starlet. But what happens when 1 ios is loaded that has the file sign bug and an other that has it not?

And: The Wad Files cant be installed because the file sign bug was fixed. Its fixed in the 3.4 system menu or the IOS that is installed with 3.4?

To answer your first question: nothing. People use the IOSs with the bug to install content. They ignore the other IOSs.

Only WADs that contain channels cant be installed without the bug. WADs can containing system files (sys menu, IOSs, etc.) can still be installed.

Also, the term is fakesign bug not file sign bug.