* formhelper.enabled
* formhelper.autozoom.enabled
* formhelper.restorezoom.enabled

What I've noticed is that I can't seem to run fennec1.1b1 build 2, directly after uninstalling a fennec 1.93 trunk build, unless I restart the whole maemo os

https://developer.mozilla.org/En/Mobile

Overriding extension compatibility can be done, by adding extensions.checkCompatibility.1.1b=true to about:config
Plugins can be enabled by setting plugin.disable=false in about:config.
You need to restart Fennec to take that change into effect.