yes but the backup option in settings just backup apps list not app data, and yes before hard reset make a backup of all your images, videos and music on a computer .
Asphalt 7 is one of the few games that backup game progress to the cloud. I have uninstalled and re-installed the game a few times, and after a few restarts of the game my progress was back.
automagically, yes
NOTE: I know that Asphalt 7 has this feature, I am not sure about Asphalt 8
automagically, yes
NOTE: I know that Asphalt 7 has this feature, I am not sure about Asphalt 8