I am wondering if it is possible to update qml android application remotely by changing qml file. To do this :
Qml should be read from the filesystem of the device dynamically instead embedding into the apk.
Is it possible?
Yes it is possible, you will only embed a small loader, possibly including an updater into the APK, which can load a QML file from the device filesystem.
On startup you can check for a new version, if available download and save it and only then load the QML file.
Note that for any non-trivial application you will most likely need to define external files as an external module so you can have your custom external types resolve properly.