[Updated] What you need to know about Tizen 2.4 OS upgrade for Samsung Z1

Update: Some items in the Important points sections have been updated.

Tizen 2.4 Operating System (OS) for the Samsung Z1 has been in beta testing since the end of September 2015. Since then there has been a huge user demand for the Operating system to mature and flourish into a final release.
We reported a few days that the Tizen 2.4 final release for the Z1 will be on or after 22 26 January in India. There is now confirmation, from Insider sources, that Samsung is looking to also release the update to Z1 users in Bangladesh, Nepal, and Sri Lanka about one week later than India.

Important Points

India release is scheduled for 22 26 January or possibly later, available to all Tizen 2.3 users
If you are a Tizen 2.4 Beta tester with version COI5 you will have to revert back to the latest official Tizen 2.3 version using KIES. We DO NOT recommend using ODIN.
If you have Tizen 2.4 version COL5 or COL6 you will receive a Over the Air (OTA) update that will take you to the final version
Other markets such as Bangladesh, Nepal, and Sri Lanka will get the update about one week later than India

New Features in Tizen 2.4 for Z1

Messages

Enhanced messaging
Pin conversations
Lock messages
Quick view of messages

Smart Manager

Smart manager app
Ultra data saving mode

Image editor

History(redo, undo, original view etc)
Portrait
Tone(Detailed modification of Brightness, Contrast, Saturation item)
Collage editor

Voice Recorder

Bookmark addition

Camera

Pro mode
Wide selfie
Interval shot
Quick launch

Calculator

Split Bill

Music

Record your own song

Voice Call

Profile info(Callers registered in profile sharing service are visbile in call screen eventhough they are not registered in Contacts)
Record
Quick view of incoming calls

Memo