1. Yes, you can still get free updates with TomTom HOME, such as MapShare, some voices, etc, even if you got the map from here.
2. It is NOT recommended to backup your device using TomTom HOME. Always use copy paste with Windows Explorer, which basically means backing up the complete contents of your device and saving it in a folder on your pc.
3. You can always switch maps if you have a few installed in your device. Or if you need to remove a map from the device and copy one across from your pc, that can always be done, as long as each map folder has .dct file(s) - which means they have been activated. Again, it is not recommended to use TT Home. Just do a simple copy paste using Windows Explorer.