So let's say my game/app is ~600Mb (.apk file) and I released it in Oculus Store. As time goes by, I would like to provide updates (bug fixes, improvements, more content, etc.)
How does updating work? Would end-user have to download whole 600Mb+ every time I update my game/app ?
Yes, when Android apps are updated, the entire new .apk file is downloaded and installed over the old version. The user's data remains unchanged in a separate directory. If you need to support incremental updates, that is something you'd have to code yourself and store on your own server.