FortiOS 4 and 3g-4g modems

[Suhofruct]

Hi! I have FortiGate 50B with OS FortiOS 4 MR3 patch 18. If i am right it's the lastest version of OS what can be istalled to FortiGate50B. OS 5.0.12 doesn't support by FortiGate 50B, if I understand correctly. 

And I have 3g modem Huawei E352, also I have 4G modem ZTE MF825.

1. Am i right that 4g modems have been not supported by FortiGate 50B OSv4? Only 3G modems.

2. When I install 3g modem Huawei E352, it has been detected by FortiGate. And I can click "Dial" button, cause modem is enabled and detected. But then modem are showing state - 'Connecting...".  I found out that, if put in cli command: "diagnose sys modem com /dev/ttyusb0" and press command "ati" - then modem connected ro network!!! What is wrong? Why doesn't modem  automatically connected to network?