Hi dear,
Both WebUpdater and Garmin Express are okay to Update Firmware
The last Firmware release for your model is 4.10:
Code:
Only the registered members can see the CODE Contents. Please Login OR Register.


Let's go to your questions:
  1. Nothing has been done to improve satellite reception.
    ChangeLog reports: "Added support for a second map on an SD card"
  2. No, software mentioned above run only on Windows or MAC
  3. As said above, there is a Firmware v.4.10 released.
    If you just made a Backup is sufficient, no others operations are needed
  4. bricking Device is ALWAYS a possible risk, never say never, despite being unlikely on these models
  5. Okay