No, but they did make the app switching more seemless so it does seem like they are one app.
Show us.
Have you updated the app?
Since when? I am running version 12.1.
for the longest time Facebook said you had to use messenger, but if you just clicked install , and didn't purchase or download messenger, and then went back to the app , it let you send messages for a few days, and then you just repeated the process. this might of came back, or your Facebook app could be old
the other story i heard was if Facebook felt your phone was old, and underpowered , you were exempted from running messenger.