try this, http://www.tp-link.com/us/faq-722.html

how do you tell router is blocked? wired connection lost internet but can login router page? how about wireless from router? which connection is not stable? router or router wifi or ap wifi?

i think it is ok to upgrade the firmware released on the website.

maybe, but is this an English version product? if no, contact Chinese support at fae@tp-link.com.cn

this is wired as the date rate is good. try contact TP-LINK support and see what they will say about this.

what bandwidth your ISP provided to you? unplug the tplink and connect directly to your internet modem, will it be the same? if no, you may contact TP-Link support directly and ask for further help.