Unofficial changelog for WP8 GDR3 + Bittersweet Shimmer update:

Windows Phone 8 GDR 3

-Support for 1080p display for new devices like the Lumia 1520.
-Support for new processors.
-3 medium or 6 small tiles on a row for phones with screen resolution higher than WXGA (1280 x 768) including Lumia 920, 925, 928, 1020 and of course the Lumia 1520.
-Close apps by tapping on the X on top right in multitasking view. The icon of the app appears below.
-Custom tones for text or IM, voicemail, email and reminders (confirmed earlier by Windows Phone Central)
-Screen Rotation lock: When auto-rotate screen is off, your screen will stay in the current orientation when you rotate your phone.
Driving Mode: Turns of all notifications except texts and phone calls when you're driving. You can also turn calls and texts off completely or set Driving Mode to text and automatic reply like "Hey, I am driving right now. I'll reply you later." Driving Mode can start automatically when your phone connects to a Bluetooth device.
-Connect to WiFi in OOBE when switching on your new phone for the first time or after you your reset your phone, so you can restore your data even before connecting to a cellular network.
-Attach Office files (.doc, .xls, .ppt) and .pdf files in email.

Nokia Bittersweet shimmer firmware

-Glance Screen: Notifications in glance screen similar to the notifications on the lock screen. Choose from any of the 20 accent colours for night mode instead of just red in Amber. You can choose whether you want to keep the glance screen always on when charging, in Amber it is always on when charging.
-New apps: Nokia Camera, Storyteller, etc.

http://www.wpcentral.com/changelog-gdr3-wi...ersweet-shimmer

http://www.nawzil.com/WindowsPhone8

Meh, Nokia should've released it as an in-built feature in Glance, not as a separate app.

cannot clear it unless u format it...

see next,update got clear some of data but still it won't clear until left 100-200mb...

why need to do? I still get notification without open the app as long as it got set the background task on the setting

620 not yet. currently waiting for approval...

http://www.nokia.com/global/support/softwa...n-asia-pacific/

open the router settings and set the WiFi channel to 1~11.

on your phone, delete the saved network, search and save it again.

have you tried swapping sim cards?

set network to 3G rather than 4G?

try toggling Flight Mode?

last resort, do hard reset (backup the Apps + Settings using WiFi first, then you can restore when the phone reboots).

you may also backup your chat to whatapps server.

just access your whatapps settings > chat settings > backup

swap phone, simply login your whatapps, all your chat history will restore.

Not sure about all chat can be restoring to new phone. But same devices can restore all chat and group chat history.

Just uninstall the live lock screen should be fine.
I'm using the live lock screen and no issues at all on 1020.