You want to establish two VPN tunnels? Can you provide a topology? http://www.tp-link.com/en/faq-244.html

Sounds like compatibility issue. Did you upgrade the latest firmware? You'd better re-format router details...as it is difficult to understand what you said...

ADSL Type is ADSL2+?

Before upgrade the firmware, do you have to change DSL Modulation type? Did you contact your ISP to check the line? If it is fine on your ISP side, you may try to get a replacement under warranty.

Media Server function makes it possible to share media files such as pictures, music and videos to Windows Media Player, game console, and other compatible devices in the same local network. But you...

Which number ddi you call? Compared with 2.4GHz, it is normal that 5GHz Wi-Fi covers a shorter range. http://forum.tp-link.com/showthread.php?81227-Poor-5MHZ-Range You may try different channels for...