GDR1 foldersSome more tidbits about Windows Phone 8.1 GDR1 and this is from OEM documentation again. You can read all the GDR1 details on our dedicated Windows Phone 8.1 GDR1 page.

Music + Videos Folder replaces Music app:

By default, there is one folder on the Start screen called Music+videos, which replaces the Music app tile. The Music+videos folder contains the Music, Video, FM Radio, and Podcasts apps. This change applies to all Start tile layouts for Windows Phone 8.1 GDR1.

Because FM Radio, Music, Podcasts, and Video are part of the default Music+videos folder, these Microsoft components are no longer available as individual components that can be prepinned to the Start screen.

Folders can be backed up and restored:

The content and layout of the folder is included in the backup process and is used when restoring to a new device.

Hidable on-screen soft buttons for all other resolution that (854 x 480):

On some display types, OEMs may omit mechanical or capacitive Back, Start, and Search buttons from the phone hardware and instead let the Windows Phone OS render these buttons through software. The OS supports two types of software-rendered buttons: user-managed buttons that can be hidden or displayed by users with a swipe from bottom, and static buttons that are always visible. Below table lists the software-rendered button options for each resolution.

Display typeUser-managed software buttonsStatic (always visible) software buttons
1080p (FHD)YesNo
720p (HD)YesNo