I have seen many times that Facebook updates its app without updating from pkay store. E.g yesterday the icons were different and today I have noticed the icon's design have changed. So how does Facebook change its app remotely
Two choices:
The last update of the app contains both old and new version and it's enabled by a server side flag
As the changes are styling only and the styling (e.g. css) is loaded (then cached) from the network so it can be changed without needing to change the application