How to downgrade firmware 2.x to 1.x original firmware?

v 2.x not support login /UI on internet.

Nearly same question, but not the same reason :

How to downgrade firmware on a MyBook World Edition II :

Since I have automaticly upgrade the firmware, the ethernet interface fall down.
It falls down after 1 hour or many hours of use.
I must reboot the MyBook WorldEdition II to be able to map the drives on my Windows 7, and to make the uPnP visible.
The log writes an inifinite internet interface down, up, down, up, down, … loop.
I didn’t have this problem before the upgrade.

How to make the uPnP visible on TP-Link WR-941ND Capture.PNG

Simple. You can’t.