I don't use FTP. After upgrade the latest firmware, did you reset and reoconfigure it? Check your settings step by step. http://www.tp-link.com/en/article/?faqid=341

Nope. TL-WDR3600_V1_130829 is the latest firmware for Unifi & Maxis Fiber users. Any trouble to access internet with the firmware? If there is no problem, no need to expect for any new firmware.

How did you test? Did you log out locally before you try to access it remotely?

@HELENA102 UN stands for Universal here and it is proper for you absolutely.

Any trouble to access internet? What kinds of log are you trying to check? To select Log Level won't help? By the way, your firmware is not the latest version.

I don't because damage to the product as a result of using third party firmware will like Openwrt or DD-WRT void the product's warranty.