 
Two new updates are rolling out to those running latest Windows 10 build, Build 9926. One of these, the update KB3035129 surprisingly exposes the selection of “Build branch” in “advanced settings” as can be seen in the below screenshot. You are advised though to not select anything else than fbl_awesome1501.
As per Gabriel Aul,
@bc3tech @bdsams Just don’t change your branch from fbl_awesome1501 and you’ll stay on the right track. Looks like the latest KB exposed ux.
— Gabriel Aul (@GabeAul) January 28, 2015
KB3035129 brings fix for “Xbox Live sing in” and some other key fixes.
@GoodThings2Life KB definitely intended for you. Fixes some key things – like Xbox Live games sign in. We’ll update to fix the other issue.
— Gabriel Aul (@GabeAul) January 28, 2015
If you check now for update, your device will prompt to look for Build 9931 or 9932, but will fail.
The other update KB3035034 brings Adobe Flash security fix for Internet explorer. Read more about this here.
