How to sign out Facebook messenger in iOS

Facebook forced user to use Facebook Messenger. Facebook’s decision to strip the chat functionality from its mothership mobile app and instead force users to use the separate Facebook Messenger app to chat with friends has predictably led to a big backlash as iPhone owners have been bombing Facebook Messenger with one-star reviews in the App Store. Many users found that it's very hard to sign out after signing in with Messenger app.

There were few ways to signout with old FB Messenger app such as: Open messenger settings > help > click on ||| 3bars on left top corner > scroll down > log out > close the app > open again messenger

Or

Open messenger settings > Privacy&Term > click on ||| 3bars on left top corner > scroll down > log out > close the app > open again messenger

Go to Settings/Privacy&Term to sign out does not work anymore with FB messenger update

Unfortunately, it does NOT work anymore for the latest updates of FB Messenger.
After hours of googling and reading but nothing works for me. I decided to go myself and finally I find it. Details with pictures are as follows:

Facebook messenger application sign in interface

Step 1: You need to have both FB application and FB Messenger application install in your iPhone. Sign in 01 identical account on both apps by:
- Login in FB application first,
- Then click on Messenger icon in the bottom center.
- Put your email/ phone number and password.

Settings

Security settings

Step 2: After signing in both apps, go to FB app and then choose More\Settings\Security
In this Security settings screen, in the last line, you will see Active Session and the number of active sessions you have in your device. Should be 2 (or more) after you signing in both FB and FB messenger apps.

List of the session you are running

Close all other session by clicking on the X symbol

Step 3: Choose Active sessions and then close other sessions by clicking on the symbol X on the right hand side.

And it is all done now. You can check by clicking on Messenger symbol in the middle. iOS will open FB messenger application, but after a few second loading, it will say the session is expired and you have to sign in again.

FB messenger session is expired, you now can sign in again your accoutn or choose sign in with different accounts.

Enjoy your facebook and keep in touch with your friends without any concerning about FB messenger sign out.
Merry Christmas and Happy  New Year