Number 4 is out of date as of Legion: Blizzard decided to cull many of the visible options, and Display Lua Errors was one of them. This completely necessitates using Bugger or BugSack, or knowing the name of the CVar to turn it on.
EDIT: Most of the culled Interface Options (those whose CVars still exist) were added to the
AdvancedInterfaceOptions AddOn.