1. The manual provided applies to your device. However, you have a legacy design router, which had hardware changes in latter iterations, due to which, it cannot be upgraded to 7.00 and newer firmware revisions.
2. You can supply power to the device from your car battery as long as the power supply voltage is within 9 - 30VDC.
3. All RUT955s are manufactured with the same modems, thus, regarding LTE specifications, there is no difference between your and current devices.