Can go to the US official website and download the US version: http://www.tp-link.com/us/download/TL-WPA4220.html#Firmware

First, it is US version if you can see there is US at the back of the device, so you need to upgrade to US version. Not sure why there are only EU version on the website, but we can send email to...

You can try to set up data usage: http://www.tp-link.com/en/faq-1679.html Or you can try to set up Access Control to control the internet access time: http://www.tp-link.com/en/faq-1687.html

Is it new? Did you put in the SIM card? Is the SIM card working on your phone? Can refer to the links below to try some troubleshooting: http://www.tp-link.com/en/faq-794.html...

Nope, but if you download the same file on another device through same wifi, will it disconnect as well? Put the PC closer to the router and get better signal, and see if you have same issue.

It will be better to purchase it from the manufacturer. Can send email to support.uk@tp-link.com and see if you can purchase the antennas from them.:)